THE ANALYST. 39 REVIEWS. PUBLIC WATER SUPPLIES. F. E. TURNEAURE and H. L. RUSSELL. New York: This book is primarily concerned with the engineering side of the question of public water supplies, but it necessarily includes a consideration of the quality of the water obtained and supplied, and this involves a chapter on the criteria provided by chemical and bacteriological methods for determining the purity of a given source. It is evident that, as the whole section touching on this topic occupies less than 100 pages in a, book of more than 700, nothing elaborate or exhaustive is to be expected. But what there is is sound, plain, and sensible, and, though not likely to be new or useful to the water analyst, will serve to guide the water engineer aright in the comprehension and interpretation of the analyst’s results.In this respect the work is commendable. B. B. John Wiley and Sons. Price 5 dollars. A MANUAL O F DETERMINATIVE BACTERIOLOGY. By FREDERICK D. CHESTER. New York : The Macmillan Company. 1901. Pp. 401. Price $2-60. This is not a text-book on bacteriology, but a work intended to be used as an analytical key to the numerous recognised races of bacteria, which has been elaborated by the author with the praiseworthy intention of lessening the difficulties which attend the identification of these organisms. The situation with regard to the successful accomplishment of the task upon which the author has ventured is one of special difficulty, for not only is the number of recognised forms of bacteria to be dealt with very large and their descriptions widely scattered, but, far more difficult than this, the nature of many so-called ‘‘ species ” of bacteria is too variable, or ill- defined, to admit of exact description, and consequently of accurate identification. It is possible to overcome the first-mentioned difficulty in a satisfactory manner, and the author has accomplished this part of his task at the expense of much time and labour, with the happy result that his book contains a very useful description of some eight hundred organisms.But regarding the ill-defined nature of many so- called species of bacteria, it is impossible for any method of identification to be a complete Ruccess, because we have not at our disposal at present the requisite know- ledge to differentiate accurately numbers of different forms of bacteria-in fact, it is, perhaps, questionable how far we can accurately use the term ‘‘ species ” in con- nection with any of the recognised bacteria.For instance, the two well-known organisms B. coli comrnuitis and B. typhosm are types possessing marked character- istics by which they may be readily identified, but between these two types there is a chain of races connecting these two ideal species, whose characteristics are so indefinite that they cannot with certainty be classed with either. I t is not the fault of the book, therefore, if it does not solve such difficulties as this, for it is limited by our present want of knowledge. But, as the author proposes in difficulties such as the one mentioned, it is possible even now to arrange a system of groups in which all doubtful organisms may be placed, even if they cannot be further identified at present.We hold that the science of bacteriology with regard to the questions of species and of means for their determination must be considered as occupying a tentative position, and if the book under notice is viewed in this light we have no40 THE ANALYST. hesitation in recommending it as a most useful work. We have tested it ourselves, and believe that if it is used carefully it fulfils its object of assisting in the determina- tion of bacteria, so far as they can be determined, in a very successful manner. But here we should like to add the caution that it is essential that those who use this book should be well prepared by previous training in bacteriological methods, for bacteriology resembles all the other experimental sciences in demanding experience from its followers.In general arrangement the book consists of two short chapters, introducing the author’s systematic list of bacteria, which occupies the rest of the volume. The first chapter treats briefly on the morphology of the bacteria, and requires no special remark; but the second chapter, which deals mainly with conditions of growth, is of special interest, for in it the author has laid down the standard conditions under which bacteria should be grown, in order to study their characteristics in a systematic manner. The author’s list of bacteria is classified according to the order proposed by Migula. It may, perhaps, be satisfactory from a botanical point of view, but we do not consider the author was well advised to follow closely any botanical classification, in view of the general purpose of his book, which is to assist in determining species and not in classifying them.There is a danger under such circumstances that simplicity in determination may have to be sacrificed at times to the less important purposes of classification, and we are inclined to think that this is shown with regard to the organisms classified by the author under the genus Mycobacterium. These organisms, as a genus, are difficult to differentiate from the genus Bacterium, and we think if they had been united under one head it would have simplified and improved the author’s system of determination. It is desirable, also, to d l attention to another point in the book which is confusing to the reader. The manner in which the author’s classified list of bacteria is introduced on page 55 is very badly chosen. This list is the main feature of the book, and occupies more than three hundred of its pages, but it commences in the middle of a page, without any special heading to call attention to its importance. These faults, to which we draw attention, and others we have noticed, are, however, of minor importance, and do not seriously impair the real value of the book, which we confidently recommend to all who have to overcome the difficulties of identifying unknown bacteria; but, as we have attempted to show in this review, the book must not be expected to act as a guide beyond the limits of our imperfect knowledge concerning the specific distinc- tions of these micro-organisms, and it can only be used with advantage by those who are skilled in bacteriological methods. A. J. B.