FOOD AND DRUGS ANALYSIS 17 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Comparative Study of the Proteins of the Colostrum and milk of the Cow and their Relations to Serum Proteins. C. Crowther and H. Raistriek. (Biochem. J., 1916, 10, 434-451 .)-The chief proteins of cow’s colostrum and cow’s milk were isolated, and ctnalysed by the method of van Slyke, with the following results : Caseinogen, total lactoglobulin, and lactalbumin are sharply differentiated and distinct proteins, and have respectively the same composition whether prepared from colostrum or from normal milk.The presence in milk of a globulin in small quantities (0.03 per cent isolated) was proved. Eulactoglobulin and pseudolacto- globulin are identical as far as the protein part; of their molecules is concerned. Lactoglobulin from either colostrum or milk is very closely allied to, and is probably identical with, serum globulin from ox-blood.Lactalburnin from either colostrum or milk is very different in composition from serum albumin from ox-blood. H. F. E. H.18 AB8TRACTB OF CHEMICAL PAPER8 Reactions of Peroxidase purified by Ultrafiltration. A. Bach. (Arch. 8ci. p h p .nat., 1916, [iv.], 42, 56-61; through J. Ckm. Soc., 1916,110, i., 682-683.) w h i l s t phenol, guaiacol, quinol, and pyropllol were found to give the same colour reactions with an extract of horse-radi& and when the same extract was aubjected t o ultrafiltration in presence of hydrogen peroxide, very different results were obfained with orcinol, aniline, dimethyl- and diethyl-aniline, benzidine, and p-phenylenediamine.When o-cresol and saligenin are treated with a mixture of purified peroxidme and hydrogen peroxide, a yellow colour is produced in both cases, which changes fo brown and then to reddish-brown. Salicylaldehyde only reacts when the solution is made slightly alkaline with hydrogen-potassium phosphate. Salicyljc acid gives no reaction. Ii the oxidation of 0-cresol and saligenin, formic wid is produced, but no appreciable amount of carbon dioxide can be detected.Ethyl alcohol is not attacked. It is considered more probable that ethyl alcohol is oxidised by a mixture than by a specific “ alcoholoxidase.” Examination of Certain Methods for the Study of Proteolytic Action. H. C. Sherman and D. E. Neun. ( J . Amer. Chem.Soc., 1916, 38, 2199-2216.)- The experiments recorded were all carried out with preparations of commercial pepsin and trypsin, the following methods being employed: (1) The Mett method; (2) the estimation of total nitrogen of digestion products ; (3) the measurement of increase of amino nitrogen by the Van Slyke method ; (4) the titration of the acidity of acid cleavage products (Volhard Lohlein method) ; (5) the increase of electrical conductivity; (6) the polarimetric method; (7) the biuret reaction; (8) the triketo- hydrindene hydrate (Ninhydrin) method.In every case, with the exception of the Mett method, a casein substrate was used. In general terms it was found that the quantitative estimation of the total nitrogen (2), or of the amino nitrogen of the digestion products (3), or both, were more delicate methods of detecting profeolysis than either the biuret or the Ninhydrin reactions, and also more generally applicable as a means for its measurement than any of the other methods.All the results emphasised the importance in quantitative comparisons of so limiting the amount of enzyme preparation and the time of its action as to keep within the region in which the velocity of hydrolysis is directly proportional to the enzyme concentration.As regards the popular Mett method, it wa8 found to be quite unreliable for trypsin a t all concentrations, owing to the action of the a b l i upon the albumin, while with pepein the action is only approximately proportional to the quantity of pepsin employed a t the very lowest concentrations at which the length of column digested is too short for accurate measurement.With the second method described above it was found that the amount of digested nitrogen increamd in direct proportion to the amount of enzyme used to about 20 to 25 mgrms. of nitrogen in the case of pepsin, or 40 to 60 mgrms. in the case of trypsin, quantities large enough to be determined by the Kjeldahl method with 8r high degree of accuracy. The nitrogen is estimated in the filtrate after precipitating the undigested casein by aodium sulphate and hydrochloric acid.For the estimations by the Van Slyke method the “ micro ” apparatus, using the new 3 C.C. gas burette, was employed. The pohrimetric method was found to afford a delicate means of detecting the action of very small amounts of proteolytic enzyme, but the fact that the change in rotationI I39 0 V L a 0 9 L 0 U 138 137 136 135 134 t33 132 131 130 I29 '12 8 127 126 125 12 4 123 122 121 120 i 19 118 8'17 112 1 1 1 110 109 108 106 105 I04 103 102 r 01 100 99 98 97 36 95 194 '93 '92 92 9 0 89 ' 8 8 87 8 6 85 8 q '8 3 82 81 Boiling Point o f Last 5 0 c.c.Boilmq Point o f Last 50 C.C.0 1 rn L t i," 0 L 01 tj 0 <I- 0BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 19 does not proceed progressively with the amount of enzyme or its time of action neoessarily renders its use for quantitative work of little or no value. Neither the biuret nor the Ninhydrin reaction ist susceptible of yielding more than rough com- parisons of proteolytic power within the range covered by the colour changes, even when the greatly enhanced delicacy obtained by the Herzfeld modification of the latter is taken advantage of (Biochem. Zeitsch., 1914, 59,249; J .Biochem., 1915,20, 217; 1916, !&, 503. See also Long and Barton, ~ A L Y S T , 1914, 39,551). H. F. E. H. General Method of Estimating the Relative Turbidity or Opacity of Fluid Suspensions including Bacterial Emulsions.G. Dreyer and A. D. Gardner. (Biochem. J . , 1916,10,399-407.)- The procedure adopted embodies the main features of the method employed by Dreyer and Hansen in an investigation dealing with the effect of light on enzymes (Cmpt. rend., 1907, 145, 564). The method is of general application for all chemical and biological measurements of turbidity, and, as described in the present paper, is concerned specially with the standardisation of agglutinable cultures.A. graduated series of dilutions of each fluid is made in miniature test-tubes of uniform bore, clean and free from scratches. By artificial light against a black background the turbiditjes of a number of tubes of one series are matched against a succesr;ion of tubes of the other series. Each reading pro- vides figures from which the relative turbidities can be calculated, and by taking the average of a number of readings, an accurate ratio is obtainable. Special details are given of the method of cdculation, and the method is shown to be capable of great accuracy in the estimation of silver in high dilutions when precipitated as silver chloride, as well as for the comparison of bacterial growths in broth, etc. H. F. E. H.