摘要:

XLV.-RICHAERD WILLSTATTER. " For all $iMf als. grass "-1 PETER i. 24." A child said, What is the grass? fuelling it to me with full hands; How could I answer the child? I do not know what it is any more than he.I guess it must be the flag of my disposition, out of hopeful green stuff woven. " Or I guess the grass is itself a child, the produced babe of the vegetation.Or I guess it is a uniform hieroglyphic And it means, Sprouting alike in broad and narrow zones. " And now it seems to me the beautiful uncut hair of graves."WALT WHITMAN, Leaves of Grass CHEMISTRY is both a craft and an art, one of V-' the finest of arts-perhaps the art of arts, a veritable " sword of Aklis," wherewith the threads are cut which hold the secrets of our material world and the nature and character of its component units disclosed; it has a wondrous psychology of which but few as yet have gained feeling, mastery and reverence. A science only in the second degree, because so much of its burden cannot be quantified, chemistry is none the less a premier science, through the exquisite finish of the enviable craftsmanship exercised by the men of genius who have been successful in its service. Among the craftsmen who have most adorned our ranks, we can place none higher than the subject of this memoir, for he has reached to the highest pinnacle of technical proficiency to which our art has been carried. A striking feature in his conquests has been the sureness and swiftness of his approach, the courage of his attack and his deft handling of situations which previous workers have failed to master.A biographer writes: * " It is an open secret to the few who know it but a mystery and a stumbling block to the many, that Science and Poetry are twin sisters: insomuch that in those branches of scientific inquiry which are most abstract, most formal and most remote from the grasp of the ordinary sensible imagination, a higher power of imagination akin to the creative instinct of the poet is most needed and most fruitful of lasting work." The chemist who can teach so much of grass, who can go so far towards answering the question put by the child to which the poet confessedly had no answer, who can also lay bare the secret of colour in flowers, may be placed even above the poet. The poet but deals with the superficial and with fancies; at best he is a mere painter. The full beauty of Nature, the structure of her wondrous mechanism, is patent only to the chemist: he is fast learning to interpret her ' uniform hieroglyphic ' in terms which admit of no dispute. Now that we can think in terms of the Angstrom unit, our vision is become ultra-microscopic. Our science of chemistry, in fact, is no twin sister of poetry but poetry itself and at its highest. Its mysteries are as deserving of attention and as marvellous as are those of even the densest stars. Indeed, the saga of the universe is before us in grass, if we will but read it: we know that " all flesh is as grass." The alphabet in which the story is told, in reality, is one of remarkable simplicity and that so few care to make the attempt to master our shorthand, the language in which our story of flowers is told, is surprising, to say the least. The outward beauty of the flower is patent to every one-the inward beauty of its mechanism, to the seeing eye, is marvellous beyond compare-the man who has done so much to interpret its character may well be deemed worthy among us.Richard Willstatter was born in Carlsruhe (Baden) on Aug. 13, 1872. At first, he was educated there but afterwards, on removal of his parents to Niirnberg, at the Realgymnasium of that town. When eighteen years old, he entered the University of Munich, where he began the study of chemistry under the great Adolf von Baeyer, a master of laboratory craft, known to the world as the first to prepare indigotin artificially, the colouring matter of the indigo plant. The fifteen years of his career were spent there as student and privat-docent, and finally, from 1902 onwards, as extraordinary professor and head of the organic chemical department. In the spring of 1902, he was appointed full professor (ordinarius) at the noted Zurich Technical High School. After spending seven years in Zurich, in 1912 he returned to Germany to take charge of the Chemical Research Department established by the Kaiser Wilhelm Society at Dahlem, Berlin. It was here that he carried out most of his work on plant-colouring matters. Ultimately, he became professor at Munich, in succession to Adolf von Baeyer. He was elected a member of the Prussian Royal Academy of Sciences in 1915 and received the Nobel Prize in 1920. It appears to have been Willstatter's ambition, from an early stage in his career, to undertake the study of vegetable and animal pigments and he advisedly entered upon a considered course of original study to acquire the necessary technical proficiency in preparation for this task. Beginning with the vegetable alkaloids, atropine and cocaine, which he was able to prepare artificially, he passed to the study of the quinones, a class of compound to which at least a majority of dyestuffs belong. He made a notable addition to knowledge by his discovery of orthobenzoquinone. He then entered upon his great inquiry into the nature of chlorophyll. He next devoted himself to the study of the red and blue colouring matters of flowers. Of late years he has been engaged in the attempt to isolate enzymes. These, however, are only the main lines of inquiry which have occupied his attention. A German professor, especially if he be a man of established repute, is called upon to provide subjects for a large body of young workers: hence it comes that Willstatter has touched a great variety of themes other than those referred to above. He has thus been led to solve a number of problems of special interest and more than ordinary difficulty. Among the inquiries, that on hydrogenation under the influence of platinum may be referred to as one of prime importance.The studies of the green colouring matter of plants are described in twenty-four memoirs, published in Liebig's Annalen der Chemie during the years 1906-14, and in a book written in conjunction with A. Stoll (Berlin, 1913). It will be remembered of Shibili Bagara that he " prepared a rapid lather and dashed it over Shagpat and commenced shaving him with lightning sweeps of the blade (Aklis). 'Twas as a racing wheel of fire to see him." So Willstatter with chlorophyll. When he began the inquiry, the view prevailed that chlorophyll was but a group name and even that each plant might contain its specific chlorophyll. Not the least remarkable outcome of his work has been to show that, in more than two hundred species of Cryptogamic and Phanerogamic plants, the same mixture is to be found, in slightly different proportions, of two closely related compounds, which he has termed a-chlorophyll and /^-chlorophyll, the former being blue-green, the latter yellow-green. This result is surprising in view of the fact that no two animals contain the same haemoglobin, although one heematin is common to all, the globin (protein) component varying from species to species. Willstatter has further shown that, in the cell plastid, as indeed Sir G. G. Stokes first pointed out in 1864, the two chlorophylls are associated with two ' yellow' colouring matters, one the well-known hydrocarbon carotene, C40H66, the other a previously unisolated compound, xantho-phyll, C40H56O2, apparently a derivative of carotene. The Phseophycese alone also contain a third carotinoid, fucoxanthin, C4()H5606. The method of separating the chlorophyll compounds adopted by Willstatter is that originally proposed by Stokes and involves the use of more of less immiscible solvents, particularly petroleum spirit and aqueous alcohol. Being soluble in a mixture of petrol and alcohol but insoluble in petrol, a- and /3-chlorophyll are precipitated when the alcohol is washed out of the solution. The method is one by means of which the pigments may be extracted from either dry or fresh leaves as easily as may an alkaloid or a sugar. The two chlorophylls are separated by fractional crystallisation from methylic alcohol and petrol. They are usually present in the proportion of about three molecules of the a- to one of the /^-compound. Their composition is remarkable, that of the a-compound being represented by the formula C32H30ON4Mg(C02CH3)(C02C20H39).The jS-compound differs only in containing an additional atom of oxygen. It will be seen that they are dicarboxylic derivatives. Significant constituents are magnesium and the radicle C20H39 of the complex alcohol, phytol, C20H39 . OH, about one-third of the weight of the molecule consisting of this component. The condition of the magnesium is peculiar, as the metal is not displaced by the action of alkalies, though readily by that of acids. Its behaviour, therefore, is similar to that of the iron in haemoglobin. The carboxyl-free mother substance of a-chlorophyll is a complex pyrrole derivative (eetioporphyriri) and the magnesium is probably associated with the nitrogen in this complex. This derivative is represented provisionally by the formula Ge CH3-C-CH C2H6-C=C NH V- NH CH,-' CH,^Etioporphyrin is a compound of outstanding interest as it is also obtainable from haemoglobin. It is noteworthy that Fischer and Klarer have recently prepared a compound synthetically from 2:4-dimethyl-3-ethylpyrrole which appears to have the properties of Willstatter's product. That primary functions of life should be exercised, both in the plant and in the animal, by compounds of similar parentage is more than remarkable. The function of haemoglobin, apparently, is that of a mere oxygen carrier-it is little more than a gasholder. Chlorophyll plays a far more complex part, as it in some ways promotes the absorption of solar energy that is involved in the reduction of carbonic acid to formaldehydrol, CH2(OH)2, and the concurrent elimination of oxygen, in the primary process of assimilation. Willstatter and his co-workers have shown that the chlorophylls remain unaltered in amount throughout the process and that they can enter into loose conjunction with carbonic acid: possibly the connexion is established through the magnesium and the carbonic acid thus made part of the energy-absorbing system. Once formaldehydrol is produced, passage to the sugars is a simple matter: yet this must be a directed operation, as the aldehydrol gives rise to only one of the two optically opposite forms of hexose. Those who talk glibly of the artificial imitation of the life process forget these little peculiarities and limitations-and so mislead the public into unjustifiable beliefs. Whatever the process, there is no reason to believe that carbonic acid is more than half reduced and the oxygen that is liberated is probably not derived from the carbon dioxide but is formed by the electrolysis of water. The operations are carried on within the chlorophyll plastid in presence of carotene and xanthophyll, both highly oxidisable substances; it is surprising that oxygen should be liberated within such a system and be without effect upon it, the more as various oxidisable materials arc formed 'within the plastid. Elsewhere, I have ventured to suggest, that the yellows serve to inhibit oxidation and thus exercise a protecting effect upon the system-an effect such as Moureu and Dufraisse have shown to be often produced by the ' interference ' of substances which are oxidisable separately but in admixture, apparently, are unaffected by oxygen.The statement is made in Sir Frederick Kceble's recent work on " The Life of Plants " that "The wheat plant alone, producing as it does a world crop containing some 70 million tons of carbohydrate, ' handles ' each year about 114 million tons of carbon dioxide and liberates to the atmosphere over 80 million tons of oxygen. The energy-value to the plant of the carbohydrate produced during photosynthesis may be computed on the basis of the amount of heat found by experiment to be liberated when a given amount of starch is caused to undergo combustion. The combustion of one ounce of starch liberates 116 calories and it is, therefore, only a matter of calculation to discover the energy value in terms of calories of the carbohydrates of the world's wheat-crop. The heat which would be produced by the combustion of the 70 million tons of carbohydrate would suffice to raise to boiling-point all the water of an ice-cold lake four miles long, four broad and of an average depth of forty fathoms."As all plants, through their leaves, exercise a similar activity, chlorophyll does some work in the world-we, therefore, might well learn to look upon it with respect, even take some little interest in its character and functions. Of what value, however, is colour in the flower? Who shall say what the significance of colour may be? We are most of us alive to its aesthetic charm and value-what of insects: are they? If attracted by it and the fertilisation process be in large measure an outcome of such attraction, then indeed it is of utmost consequence to life.The patterns of the colours in flowers have been deciphered with surprising skill and surprising swiftness by Willstatter and he has shown, more over, that they are of remarkable simplicity. He has dealt with the reds and blues, which he has termed anthocyans; the yellows have been fairly well studied by others. In many plants, yellow and orange are due to xanthophyll and carotene: in other cases, they are mostly traceable to the presence of hydroxy-derivatives of flavone, present as a white meal upon the leaves and flower stalks of many of the Primulacese. Flavone, as shown by Hugo Muller, may be resolved into acetophenone and salicylic acid-two simple substances: OH C6H5 CBH5 + CO + OH.,= COOHThe anthocyans are mostly glucosides, yielding on hydrolysis either glucose or galactose or rhamnose together with the coloured component or anthocyanidin, which in some cases is a methylated derivative. They are resolved by the action of alkali into the trihydroxybenzene, phloro-glucinol, either parahydroxybenzoic, protocatechuic acid or gallic acid or maybe a methylated derivative of one of' these. The parent substance may be formulated as an orthoquinonoid derivative, thus: HO/N/°V-/~~\ Y t! COH HIn many respects their properties are peculiar but it is impossible to discuss them here. The reds are but acid forms of the blues. As in the flavones, the intensity of the colour increases with the number of hydroxy groups in the lateral phenyl group. Much might be said on the relation of colour to structure in these compounds were space available - no more fascinating subject could be entered upon. Willstatter's work has of course been followed by a synthetic repercussion. In recent years, Prof. Robinson, in Manchester, has most skilfully developed methods with the aid of which it is possible to prepare anthocyanidins in the laboratory in any desired quantity: so to-day we can paint the lily with its own pigments.Passing now to Willstatter's most recent work, that on enzymes, we are brought into a troubled field, one which, however, we must contemplate with wonder, as their activities lie behind the mysteries of life. The colouring matters of plants appear to be without functional significance-they seem to be mere dress effects. Chlorophyll, however, is life at its outset, as by its agency the bricks are shapen which Nature hands to the plant: not only so, for with its aid energy is captured from the sun, which the plant not only uses to its own ends but also passes on to us. What of the enzymes, Willstatter's latest subject of study? Life, we know, in the main involves only two processes- on one hand, that of hydrolysis and its reverse; on the other, that of oxidation (hydroxylation) and its reverse. Oxidation, apparently, is determined and controlled by agents which are limited in their range of action but not specifically selective and, therefore, are not to be counted with the enzymes. The enzymes are the agents in charge of the hydrolytic process, whether this be downgrade or upgrade. They apparently are the templates which regulate constructive metabolism, both in plants and animals, for they are strictly selective agents. Hitherto they have been elusive entitis, only characterised by then: effects. Willstatter's efforts have been to prepare them in the individual state, so that they may be further characterised and their nature determined. The task is one of extraordinary difficulty. He has shown that they may be handled with far greater impunity than had been supposed and has devised methods of purifying them whereby he has greatly raised their activity but without arriving at any definite result. The final picture he has drawn for us of the enzyme is that of a colloid carrier of a group which is the active component: a picture drawn by my son and myself in 1913; indeed, we went further, in showing the colloid in attachment with a directing group, in addition. I perhaps more than any one can appreciate the value of work so varied yet always in logical connexion-can wonder at the genius displayed and the self-sacrificing devotion of the worker to his task. Only the few among us can be aware what such inquiry means, what it involves -what are its joys-what its pains. Perhaps, some day, these matters will come home, in some slight measure, to those who in the arrogance of their ignorance pretend to rule the world-I say this because I should like to think that " the flag of my disposition [is]out of hopeful green stuff woven" and that the moral value of inquiries such as have been referred to may not always remain, unknown to the public. 1 F. Pollock in Leslie Stephen and Frederick Pollock's Lectures and Essays, by W. K. Clifford.

ISSN:0028-0836    

DOI:10.1038/120001a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

TWO years age May 23, 1925, p. 793) the first edition/9T'n|f": Evans's book was reviewed by the present writer in the columns of NATURE. Its good qualities have evidently been widely recognised, since a second edition has recently been published. The author states in his preface to this that progress made during this period in the understanding of the processes of corrosion has made so many additions necessary, that it has taken him longer to write the second edition than the first. The same general arrangement has been preserved, and he has adhered to the policy of giving a concise statement of the subject in the text accompanied by numerous references in the foot-notes to papers where further details can be sought on any particular point of interest. The net result is the production of a book some forty pages longer than the original volume and the published price has been slightly increased. We learn from the chapter on the corrosion of copper and copper alloys, that an interesting protection process has recently been adopted by the Cunard Steamship Company, Ltd., which consists in spraying the interior of the condenser tubes with a bituminous composition. Austin, who has described the process in detail (Trans. Liverpool Eng. Soc., 46, 1925), states that the vacuum is reduced by j to | inch (owing to the decrease in the thermal conductivity of the coated tubes) but the over-all efficiency is not affected. Mr. Evans suggests as the reason for this, the increased cleanliness of the boiler heating surfaces and turbine blades. So far the experiment has proved very successful, only 21 tubes out of 28,500 having failed since its installation. As yet the process has not been tested in ships sailing in warm waters. The electrochemical process for protecting condenser tubes is stated to be somewhat of a disappointment, and the latest reports from many trustworthy sources indicate that in many cases little or no benefit has been obtained where it had been installed. Dr. Honegger states that in some cases the process has failed completely, while in other cases it has proved very useful. It seems quite possible that in the latter cases this has been achieved by the deposition on the tubes of a film of iron compounds derived from the anode rather than by true cathodic protection. Bengough and Stuart have pointed out that the weak feature of the method lies in the impossibility of securing the distribution of the current over the whole of the tube surface. Mr. Evans directs attention in a foot-note to the fact that there is. no fundamental reason why cathodic treatment should put a stop to corrosion and that cases are known where mild cathodic polarisation-by keeping the metal active-may actually accelerate attack.In Chapter xi., entitled " Protection against Corrosion," we notice the statement that " the employment of sodium silicate (water glass) as an inhibitor is increasing." It finds application as an addition to plumbo-solvent waters prior to their entry into lead pipes. It is used in cleaning aluminium. Both in liquid and solid form it is also being used to prevent the destruction of iron pipes by water and, in many cases, has been found to reduce corrosion considerably. In recent years the same material has been used in increasing quantities in boilers. Here, however, other questions are raised, e.g. the possible effect of the protective film (which is probably silica or a silic%te) on the heat-transfer; the possible increase of foaming and the action on the brass fittings. Further research on all these points would be of value. Hall, who has made a long study of boiler scales, points out that a calcium silicate scale has a most pernicious effect in a boiler. It is therefore not advisable to add sodium silicate to a hard water rich in calcium. It is interesting, to notice the author's statement that the electro-deposition of chromium as a protective coating is now being utilised. This metal does not adhere well to steel if deposited directly, but satisfactory results have been obtained if a thin layer of copper or nickel is first deposited on it. The chromium plating then follows, usually from a bath containing chromic acid and chromium sulphate, which must be kept cool. It is stated that plated articles manufactured in this way withstand corrosion by sea water, and also exhibit resistance to tarnishing. The hardness of chromium is a considerable additional advantage. It may be that this metal will prove a serious rival to nickel in spite of the greater expense involved. Later on in the same chapter we observe a reference to the operation known in Germany as Nitrierung, which consists in protecting iron by heating it in ammonia, a process which produces a very hard nitride layer. Actually this process is mainly applied for increasing hardness, but it does afford some protection against corrosion.Several processes have been worked out for producing protective coats upon metals by subjecting them to anodic treatment in suitable solutions. Special reference should be made to the work of Bengough and Stuart, who have devised a method for the protection of aluminium and its light alloys such as duralumin which has given most promising results. The articles in question are made the anodes in a 3 per cent, solution of chromic acid at about 40° C. The cathode consists of carbon. The applied E.M.F. is gradually raised to a value depending on the nature of the alloy and the composition of the bath. After treating for some time in this manner the surface of the metal becomes covered with a semi-opaque uniform white coating. This seems to consist almost entirely of aluminium hydroxide in a glassy adherent form. Possibly it is hydrated to some extent, but the amount of hydration cannot be large, since the coating can be heated to 350° C. without changing in appearance or density. Not only does this coating afford considerable resistance to corrosion, but it also acts as an excellent basis for the application of protective paints or varnishes which are not very satisfactory if applied to untreated aluminium. The anodic protection of duralumin is finding wide application- both in the aircraft industry and in the protection of artificial limbs against corrosion. The final chapter on corrosion-resisting materials contains the latest information on the many varieties of stainless steel and stainless iron now available. The alloy manufactured in England under the name of ' Staybrite ' contains no less than 18 per cent, chromium and 8 per cent, of nickel; the German material known as V2A contains from 20 to 25 per cent, of chromium and 6 per cent, of nickel. Unlike ordinary stainless steel, which has a duplex structure, these alloys, as Mr. Evans points out, consist of a single phase. The iron is in the austenite (gamma iron) condition. Accordingly the materials are ductile and can be wrought into almost any form. It has even been found possible to weld them. Reference may also be made to stellite, which is the most important corrosion-resisting alloy of cobalt. It is a very composite alloy containing considerable quantities of cobalt, chromium, and tungsten, and smaller quantities of iron, carbon, and possibly silicon and manganese. It combines good anti-corrosion properties with great mechanical hardness.In conclusion, it may be stated that the second edition of Mr. Evans's book is even more serviceable than the original volume, and the demand for it will probably be at least as great. We hope it will be even greate

ISSN:0028-0836    

DOI:10.1038/120005a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE project of an art of night, analogous to music, threatensJ^a become an obsession, recurring in evcfijy, .generation, attacking indiscriminately philosopher, artist, and empirical scientist. It is particularly insidious because it cannot be flatly dismissed as a mere chimera. There may be something in it, and there is no alternative but to think the matter out. Other than Major Klein probably no one has combined so firm a belief in the possibility of this art with so comprehensive a group of the relevant scientific data, or with so frank a recognition of the difficulties in the way. His work will certainly rank for a long time as the standard authority on the subject, and it leaves no excuse for future exponents ignoring their predecessors' errors. An enormous amount has gone to its compilation. Approaching the question from an historical point of view, the author has studied every important contribution, examined every instrument, and canvassed every opinion. (The bibliography ranges from Aristotle to the provincial press reports on the touring colour organ.) Not every opinion is equally important, and the author would not have been blamed if he had dealt more fully with some of the central issues at the expense of some of this historical material. But even in the bewildering byways of speculation he himself is critical and alert.Theoretically, the abstract possibility of an art of light is reasonably established. Colours presented in succession can produce a definite aesthetic effect. But this is obviously not enough. Pyrotechny is a sort of art of light; but what is projected is something more profound, something really comparable to music. This is a further and more difficult issue, raising a host of technical, practical, and aesthetic questions. Scientific interests enter in two ways. First, adequate theoretical foundations must be secured. The physical properties of the spectrum provide a tangible starting-point, but the scales of colour must apply to every dimension of the colour octahedron (or whatever schema is ultimately adopted) and must be empirically determined with due regard to the individual variations of differential threshold, and for all the facts of colour sensitivity arising from the peculiarities of the cerebro-retinal mechanism. A technique for estab lishing such scales is, of course, at hand in Fechner's psycho-physical methods, but scales so established would not imply ' intervals ' of the type required. On this crucial point the whole inquiry has been given an unfortunate twist by two curious phenomena which, in virtue of their peculiarity rather than their importance, have impressed the imagination of most inventors of an art of light. One of these is the psychological curiosity of syn-sesthesia; the other is the, after all, surprising fact that harmonious ' intervals ' experienced in awareness of tones are physically paralleled by certain simple ratios between the frequencies of the vibratory stimuli. The combined effect of these two facts has been to foster a number of fruitless attempts to accompany music by synsesthetic lights or even to translate music directly into colour, and to encourage a great deal of specious but wholly unconvincing argument to establish harmonic colour scales on the basis of the ratios of the frequencies of waves of light.It is one of the solid merits of Major Klein's work that he refuses to be ensnared in this inversion of the natural and logical order of investigation. After a careful analysis of these theories he comes unambiguously to the conclusion that the intervals of colour must be independently established. Independently established, but how? The author, it seems, is not enamoured "with the method of paired comparisons, preferring to await the birth of a colour musician who will divine the laws of colour harmony by the unaided light of Nature. That would be eminently desirable, but the point is, we rather urgently require some preliminary evidence that the laws are there for him to divine. What we know at present with regard to the harmony of co-presented colours cannot (owing to the factor of spatial configuration) be applied sim-pliciter to colour sequences. The fact that no adequate research has been directed upon the problem of colour ' mefBidy ' constitutes a serious weakness in the theoretical foundations of this art. A second strain of purely scientific interest enters in connexion with the provision of technical devices for the control of colour stimuli. For good, though not conclusive, reasons, Major Klein has committed himself to a policy which will engender serious practical obstacles to the cultivation and diffusion of the projected art. He requires a specially constructed hall and an elaborate type of projecting spectroscope controlled by a keyboard embodying the principles of the theoretical colour scales. Now, the art of sound has had the advantage that the human organism is itself a musical instrument and potent instinctive tendencies have motivated its use and exercise. Per centra, the art of light lacks this natural basis-and simple instruments fail to achieve any very impressive effects. But even a tom-tom or a simple pipe can produce a distinct effect, and without them we should have had neither orchestra, composer, nor audience. Inventions of the art of light have pursued many analogies, but not the biological. What is the counterpart in colour music to the folk-song or the country dance? When his instrument is to cost £10,000, how is the colour musician to acquire facility in his art? Perhaps the failure of simple instruments points to a certain weakness in our reactions to mobile colour. The emotional possibilities may be too limited to support a vital art, and some centuries of further cultivation may be required. Perhaps, too, the author has unwittingly aggravated his difficulties by applying to a new and infantile art aesthetic theories derived from modern and sophisticated spheres. But on aesthetic theories each man may hold his own opinion, and these at any rate fall outside the scope of the present review.The objections are not final. To prophesy a negative is as difficult as to prove one; and a new approach may completely change the situation. In any event the author has performed a useful service in presenting the problem in a clear and definite way

ISSN:0028-0836    

DOI:10.1038/120007a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

(1) WE have already dealt with Parts 1-8 of this V V work, and now that it has reached completion with Part 13, including an author and subject-matter index, it seems desirable to review the entire work. The first edition of " Die Fermente " appeared as quite a modest volume twenty-five years ago, and since that time the immense amount of work which has been carried out on the subject of enzymes has necessitated the publication of several fresh editions, the task culminating in the compilation of the present extensive treatise, dealing in an exhaustive manner with what is now one of the most important branches of biochemistry. The last edition of Prof. Oppenheimer's book has been out-of-print since 1918, and it was decided by the author to recast the whole work, retaining only here and there those portions of the previous text, without altering its general plan. In view of the large additions to our knowledge during the past decade, it has been found necessary to omit some of the older observations, which in the opinion of the author are obsolete. In adopting this course he points out, however, that he has paid due regard to the necessity of preserving the character of the work as giving a complete account of the subject.We know very little at the present time concerning the chemical nature of an enzyme, but as a result of the most recent work, among which that of Willstatter stands out prominently, enzyme preparations have been purified and their activity thereby increased enormously, whilst at the same time some of them have given indications that they consist of chemical entities. But in all probability an enzyme will be found to constitute a system rather than a single chemical substance. In this connexion, however, attention may be directed to the recent work of Sumner (1926), who shows that a crystalline globulin from jack bean exhibits the activity of a urease. He states that it may be recrystallised by solution in water and addition of acetone up to 30 per cent, concentration and gradual treatment of the solution at 0° with potassium dihydrogen phosphate of pH 6-1. Here, however, we have the presence of the phosphate to be taken into account, which probably does something more than adjust the hydrogen ion concentration. What may be called the nucleal part of this system is the zymogen, which under certain conditions is rendered active. The chief of these conditions is the hydrogen ion concentration arid the presence of certain electrolytes. Machaelis regards enzymes as amphoteric electrolytes or ampholytes; and this theory, developed by Bjerrum, is dealt with fully in the treatise. The entire work is spread over 2037 pages and is divided into two volumes. The first volume, covering 775 pages of text, deals with the general chemistry of enzymes, the kinetics of their actions and the biology of the subjects, the concluding v part of the volume being devoted to the esterases {lipase, etc.), the carbohydrases, and the nucleases. The second volume is concerned with amidases, aminoacidases, proteases, and a group of enzymes connected with oxidations and reductions, to which ""o the author has given the name desmolases, including zymase, the various oxidases and autoxidisable substances such as glutathione.The author classifies enzymes according to the ov substrata on which they act: thus esterases, including the lipases, carbohydrases, proteases, and desmolases, including zymases and the respiratory enzymes. He admits that if in the future some knowledge be forthcoming of the constitution of a given enzyme, a fresh classification will have to be elaborated. In this connexion we may quote his remarks: " It can only be hoped that the work on the chemical nature of the ferments which Will-v statter has so happily inaugurated, will lead to clear and definite results. If the structure of one of the ferments is cleared up, this will soon be extended to the whole class, just as with the hormones as exemplified in the case of adrenaline," and he might have added thryoxin, which, however, has been synthesised by Harington since the publication of this treatise. Under physical chemistry and kinetics, ultra-filtration, kataphoresis, complexes with heavy metals, surface tension and adsorption phenomena, and reciprocal precipitation of colloids are discussed. Reaction velocity and catalysis are fully dealt with. Discussing the thermochemistry of fermentation, it is shown that the theoretical "* quantity of heat envolved per gram molecule of glucose fermented is 28-2 K, whereas Riibner found experimentally 24 K. No reference is made, however, to the determination of the heat of fermentation of maltose by the late A. J. Brown, whose results were derived from practical data in a brewery.The interesting observation of Kuhn (1923) is recorded that the invertase (sucrase) from yeast (bottom fermentation) and from Aspergillus oryzce respectively behave differently towards sucrose. In the former case the hydrolysis is slackened by the presence of at-fructose, whilst in the latter case v it is slackened by the presence of d!-glucose. That a treatise of so comprehensive a character as that before us was much needed, no one will deny, but much as we value it we are bound to say that the text is needlessly diffuse and abounds with i^ repetitions. The lipase of seeds is said to be distinguished from that present in the liver and tissues of animals in being insoluble in all solvents, and this statement is repeated several times. Many other similar cases could be cited. We are surprised to find the statement that, during germination, amylase is rendered soluble without altering its functions. Amylase of raw grain (barley) is probably partially insoluble, and the maltase which accompanies it is insoluble, but amylase of germinated grain will act on amylopectin, whereas that of raw grain merely depolymerises it.The best way to judge a book of the kind before us, however, is to use it, and it gives the present writer pleasure to state that he has found the treatise invaluable as a book of reference on which to base his lectures on enzymes and to serve as a guide to original papers on the subject. (2) The authors have prepared this work from the larger treatise " Die Fermente," of which it is a shortened edition, to serve as a students' manual. That such a manual was needed there can be- no doubt. However, the text of the larger treatise has been to a great extent retained, the difference being that whole parts have been excised and that fewer references are given to the literature. The names of those responsible for the observations cited in the text are given in some cases without references. In our opinion it would have been much better if the work had been entirely re-cast, as it would then have been possible to reduce the size of the volume considerably and to obtain a better logical sequence in the text, which is specially desirable in a book intended for students. The subject matters are arranged in the same order as in the larger treatise, -but many pieces of work which have appeared since the publication of the earlier parts of the latter are referred to, thus bringing the book up-to-date

ISSN:0028-0836    

DOI:10.1038/120008a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE author states in his preface to this book that his aim in writing it has been to fill the need of a simple, yet accurate, scientific account, intelligible to the adolescent boy or girl, of the phenomena of the reproduction of life. The problem of selection and presentation of material for a book of this kind is a difficult one, as any one who has had experience of teaching hygiene to school children will appreciate, and Mr. Cokkinis has not been very successful in solving it. He has attempted to cover an unnecessarily wide field. Those sections on plant and animal reproduction, in which he describes and figures, often inaccurately (see, for example, Figs. 59 and 69), the reproductive organs in plants, and in the more important classes of the animal kingdom, can be studied in any elementary text-book of biology, with this advantage, that they are there set forth with correctness of detail. A short account of the cellular basis of living organisms, with a clear description of the differences between asexual and sexual reproduction, oviparous and viviparous development, would have been sufficient introduction to the study of the question in man. The great difficulty which the average individual naturally experiences in visualising, with any clearness, the position and relation of the organs of the body, makes it absolutely essential that these points should be illustrated by careful, large-scale drawings. Isolated diagrams of partially dissected systems, such as are given in this book, convey nothing to the untrained mind.

ISSN:0028-0836    

DOI:10.1038/120009a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

MB. BEEBE who is Director of Tropical Research of tlyrrfe^ York Zoological Society, travelled to Ceylon, India, Burma, the Malay States, and Borneo to search for rare pheasants and to study their habits. The results of his explorations have been published in technical papers. The present book deals with a few of his adventures, and is not a connected account of his travels. The reader receives an impression of a cheerful and intrepid explorer, who was undaunted by any dangers, difficulties, or hardships. His success was probably chiefly due to his sympathy with the wild tribes who live in the remote jungles that harbour the rarer pheasants. Without their help he could scarcely have reached his goal. Mr. Beebe has generous praise for the few British who administer the remote jungle areas, and whose methods of handling the native races won his admiration.

ISSN:0028-0836    

DOI:10.1038/120010d0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN my letter on the recession of the Tahitian coral reefs published in NATURE of April 23, proof is given of the original continuity of the present barrier reef from shore to ocean slope. The absence of a lagoon from parts of the coasts of both Tahiti and Moorea should alone prove that barrier reefs can no longer be taken as an index of subsidence without independent proof from the adjacent land, and the completion of the proof that barriers may be formed from broad reefs of the fringing type should be decisive. Further, I propose shortly to publish proof that in the adjacent but older island of Moorea there has been a tilting, resulting in subsidence of the south coast, which, though it took place during the growth of the reefs, has not made any difference to their form off that part of the island. The investigation of reef problems owes much to the numerous papers by Prof. Davis, which insist upon, and explain, the geological factors which it is essential to take into account. The biologist must, however, join in these researches, and it is much to be regretted that this side has been entirely neglected in Davis's work. One also misses any detailed local descriptions of the great series of reefs, old and new, which he has visited, that of Tahiti being the only one I have seen; this appears in French inAnnales de Géographic, 1918. In this Prof. Davis gives reasons for believing that the island has undergone a large subsidence, with which conclusion, after much consideration given to the subject on the spot, I am quite unable to agree.The evidences given are (1) the flats at the mouths of valleys, (2) certain bays on the south coast The former is inconclusive, the latter wrong in fact. The figure given of one of these valley flats, apparently the Reine Valley just west of Papeete, shows a practically sea-level flat penetrating far into the hills. In fact, the largest of these flats goes but a few hundred yards inland, and in no case is it level, all the streams having a rapid flow throughout their course. It is also interesting to note that two of the largest flats are partially cut off from that outside the line of the old marine cliffs, by spurs projecting across the valley from one side. This is not shown in the figure given, but its presence very greatly reduces the extent of the flat which can be regarded as a drowned valley. The evidence from these flats leaves the question open, unless corroboratioii can be found elsewhere. This is supposed to be found in (2) the bays of the south coast, which failing, we are justified in adopting the explanation of the formation of the flats which Davis mentions only to dismiss, namely, the wanderings of the streams from side to side of their valleys when they find their exits more or less blocked by beaches thrown up by the waves, or by incipient coral reefs. (2) There are no bays in Tahiti or the peninsula of Taiarapu. I am surprised to see that Davis quotes ' Port Phaeton,' on the west side of the isthmus which joins the two volcanic cones, and certain much smaller which are connected with it. Now Port Phaeton is not a bay in the ordinary sense at all, being merely the space left between the two volcanoes which is closed at the east end by the isthmus, which is mainly formed by a long lava flow from the southern and smaller cone. This space is further narrowed into a valley-like outline by the growth of reefs, and the alluvial flats which they support. It seems extraordinary that this origin of the bay should have been overlooked, since it is patent that there never was here a stream large enough to cut what would be the broadest valley in the islands.The little bays which open out of Port Phaeton on either hand are very peculiar, but consideration of their formation requires more space than is at present possible. They are certainly not drowned valleys, nor ordinary stream valleys at all. Those not filled by alluvium or marsh are extremely shallow, while some of those on the south side of the ' Port' are merely patches of reef, covered with a foot or two of water, which were left when most of the surface was converted into land by banks, some of alluvium, others of coral debris. (3) Charts of the whole coast of these islands have been made with great detail arid accuracy, and on a large scale, yet no scrutiny has revealed submarine evidence of submergence.I also regret that Prof. Davis did not combine his geological observations with detailed examination of the reefs, and so discover how very partial, and even inaccurate, are the accounts given by his predecessors, whose views he discusses at length. He personally examined the undersea banks within the reef, which is evidently what I term the submerged flat, but there are two important mistakes in his description. The bank is not mainly composed of sand, which covers coral rock thinly and is often absent altogether, and, of the hundreds of the blocks of stone with which they are strewn and which I have examined, all are colonies of the coral Porites, more or less dead and often much decayed. They are not " arraches au recif par les vagues de tempete." Though sometimes moved about, or thrown ashore where the barrier affords no protection, they all grew in this part of the lagoon, and they are never found on the outer slopes. There are no ' negro heads ' on the actual edge of the reef anywhere, and I know of only four pieces of reef rock which have been tossed on to the surface from an overhanging edge. Porites colonies are common on shore reefs exposed to heavy surf, though judging from the slowness with which they blacken and decay, the addition of another to their number is a rare event. The origin of the lagoon by the hollowing out of a once continuous reef is dealt with as follows. " But the hypothesis of the formation of the lagoon by the progressive dissolution of a reef continuing to develop on its outer border is in contradiction with the luxuriant growth of corals inside the lagoon, where it forms little islands, and with the deposit observable in many places in the lagoon, of debris brought from the reef and volcanic materials of the island." Coral growth, in most of the Tahitian lagoons, is greatly restricted. It is conspicuous near Papeete as the reef surfaces are covered in a remarkable way with corals, but there is practically none at all on the side of the reefs, and the long projecting shelves, which have been taken as evidence of rapid extension, are exactly the reverse. That the lagoons are slowly shoaling may be admitted pending proof; that they are becoming narrower is certainly untrue in many cases, doubtful in others.Tahiti is not unique. Moorea differs in several ways but is a variation of the same type. Davis seems to have missed the cliffs of the northern part of this island, which are equally evident, and on the northwest are higher than the average of those of Tahiti. His criticism of Daly's theory of glacial control therefore fails in this case. The four other islands visited are not described, and of their structure I can give no information. They are all older, and probably, as in Rarotonga, their cliffs have been disguised by subaerial denudation.Much exploration remains to be done in this group, which I should consider myself fortunate to be able to attempt

ISSN:0028-0836    

DOI:10.1038/120011a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT may seem scarcely sporting to intervene in a discussion between two such masters of controversy as Dr. C. Walker and Prof. J. S. Huxley, but there is a danger that ordinary biologists, in watching the clever play of these two duellists, may overlook the fact that the Mendelian theory so skilfully wielded by both is really a powerful weapon for the attack of biological problems.Dr. Walker recognises that in many cases " the usual mode of distribution of the chromosomes between dividing cells before " (and after?) " fertilisation, provides a perfect mechanism for the distribution of ' genes' . . ." He then proceeds to criticise the ' Neo-Mendelian ' theory on account of some apparent exceptions to this method of distribution, but this appears to be a hypercritical attitude. Exceptions are said to prove rules, and this " distribution of the chromosomes " is present in most cases of fertilisation. The exceptions are extremely interesting, of course; they should be and are being investigated, but what is the explanation of the normal behaviour of chromosomes before and after fertilisation? Dr. WTalker would not claim that these very peculiar processes of reduction and fertilisation are present merely to mislead investigators, but he seems to think that they appear to be a perfect mechanism for the distribution of the genes and yet are not really such. - The transmission of paternal characters by the spermatozoon is not denied by Dr. Walker, and if he doubts the transmission of these characters in some way through the chromatin material of male sperm cell, there is very little left in the sperm. That would appear to make the problem more difficult still, and unnecessarily so. Admittedly it is difficult to imagine the potentialities (or half of them) for the development of an animal as being contained in the microscopic spermatozoon, but the facts of heredity indicate that they actually are. Then is it much more difficult to believe that these potentialities are arranged in some sort of order in the individual chromosomes, since we know that both the potentialities and the chromosomes are there? The work of Morgan and others tends to show that certain facts in heredity are most easily explained by adopting such a theory, and there is no inherent impossibility in it in most cases, only there are apparent exceptions or difficulties in some instances which certainly require explanation, but these need not be regarded as fatal to the whole theory.Dr. Walker objects to the expression ' law ' instead of ' theory,' and there, of course, most would agree with him. Taught by past painful experiences most scientists to-day would refer to any attempted explanations of natural phenomena as ' theories,' not ' laws,' but by all means let us make use of these theories so long as they are useful.

ISSN:0028-0836    

DOI:10.1038/120012b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

SINGULARLY little seems to be known as to the extent to which radio (wireless) waves will penetrate into the ground, and yet information on this very point has become quite desirable inasmuch as there are now two or three geophysical methods of ore prospecting which definitely attempt to use radio waves for the detection of ore beneath the earth.Experiments by one of the present writers, and others, in a mile-long tunnel at Montreal have indicated clearly that 40-metre waves could not be detected, at either end, when only a few hundred feet within the tunnel. Broadcasting waves (400 m.) appeared to do better and were detected, with the help of good amplification, throughout the tunnel under an overload of 700 feet of limestone and igneous rocks. Longer waves (10,000 m.) were detected yet more readily. But it remained uncertain whether these waves came into the tunnel through the air, or along the rails and electric wires, or whether they came through the rock. The only sure thing is that the 40-metre waves did not penetrate to the centre of the tunnel by any of these means. Experiments by the U.S. Bureau of Mines, at a mine near Pittsburgh indicate similar results, for although initial experiments seemed to point to the passage of radio waves through rocks, yet further experience showed that rails or wires were acting as carriers. Experiments with submerged submarines prove that radio waves will not pass more than about 50 or 60 feet into seawater, no matter what the wave-length. But the question of penetration into fresh water, damp rock, and dry rock remains uncertain. More over, in ore prospecting, distances are used immensely less than the wave-lengths employed, and it has been asked whether we have to contrast radiation and induction, a convenient distinction well brought out in Bellinger's paper (" Principles of Radio Transmission," Sci. Papers, Bureau of Standards, vol. 15, p. 441), although of course at a given point and instant there can be but one electric vector and one magnetic vector.The real object of this letter is to express the hope that some wireless enthusiasts may have the opportunity of making experiments underground in cave, tunnel, or mine which is absolutely devoid of wires or other conductors, and where the windings from the entrance are sufficiently devious to preclude the passage of waves through air down to the receiving apparatus consisting of coil, amplifier, and receiver only. Accurate measures of signal intensity would be still more valuable.

ISSN:0028-0836    

DOI:10.1038/120013a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT may perhaps interest some readers of NATURE who are concerned with the study of tropical timbers, to know that a certain number of duplicate timber specimens from the Burma type collection are available for distribution to museums or research institutions.The specimen blocks, which are 6 in. x 4 in. x 2 in. in size,' have been made from trees which have been individually identified botanically, with check identifications at the Forest Research Institute, Dehra Dun, and at Kew, the original sheets being in the forest herbaria at Maymyo and Dehra Dun or in certain cases at Kcw. No charge will be made for the specimens except for packing and freight.A list of the species available can be obtained from the xmdersigncd.

ISSN:0028-0836    

DOI:10.1038/120014d0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature