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SCIENCE. 



[N. S. Vol. IV. No. 98. 



scattered facts of histology must be welcomed 

 as affording a comprehensive review of past 

 work and a firmer basis for investigation. The 

 author of this Comparative Microscopical Anat- 

 omy has made this attempt for the Vertebrata 

 and has succeeded admirably, if one may judge 

 from the character of Part I., which is all that 

 has appeared. 



The work is conceived with the character- 

 istically German disregard of difficulties and 

 long years of labor, although the author recog- 

 nizes the magnitude of the task before him. 

 Indeed, in his preface he states that his notes 

 are so arranged that his successor will be per- 

 fectly able to continue the work, if it should 

 drop from his hands. 



Part I. treats of the histology of the stomach. 

 Just why Dr. Oppel should have begun with 

 this organ is not clear. It would seem that 

 the study of the organs in some natural series 

 would preserve a more logical order. Why not 

 begin with the upper end of the alimentary 

 canal, for instance, and follow with the different 

 sections in their order ? 



A work of this nature must, of necessity, be 

 largely a compilation of facts or opinions gather- 

 ed from the literature on the subject. Further- 

 more, it is important that the authorities be 

 given, in order to avoid confusion and to enable 

 the student to refer to the original papers. 

 This end the author has had in view throughout 

 the work. As he himself states, the book is 

 intended not to replace the literature, but to 

 serve as a key to it. In his references not only 

 the name of the author is given, but also the 

 year of publication, and an empirical number 

 referring to the alphabetical index of authors, 

 where the title and place of publication are 

 given in full. The summary of each author's 

 view, whether it be a few words only or sev- 

 eral paragraphs, is enclosed between two 

 straight bars placed obliquely (//). This ar- 

 rangement aids distinctly in separating sharply 

 the work of different authorities. The typo- 

 graphical work is good, the number of errors 

 being exceedingly small. The figures are, as 

 the author states, mostly copies, some of which 

 he has found it necessary to schematise. Except 

 five lithographic plates, they are all wood-cuts 

 (375 in number) and nearly all extremely good. 



The subject-matter is divided into chapters 

 corresponding to the classes of Vertebrates. 

 Following the introduction — a short statement 

 of the purpose and scope of the work — is a 

 chapter on the general plan of structure of the 

 vertebrate stomach. The following chapters 

 deal successively with Fishes, Amphibia, Rep- 

 tiles, etc. Each chapter opens with a general 

 summary of the structure of the stomach in 

 each class, given under the various heads of 

 Epithelium, Muscular Layers, Lymphatic 

 Tissue, etc. Following this the various forms 

 of the class are discussed in their proper sys- 

 tematic order, so far as they have been investi- 

 gated. Considerable space is also given to a 

 discussion of the physiology of the glands and 

 the constitution of the gastric juice, especially 

 in the higher animals. The chapter on the 

 mammalian stomach occupies somewhat more 

 than half the book and is, of course, much more 

 complete than the other chapters. 



As the various points of theoretical interest 

 arise, they are thoroughly discussed, the author 

 in most cases giving his own views after a sum- 

 mary of the literature. An important question, 

 the phylogeny of the gastric glands, is discussed 

 in the first chapter. Oppel concludes that it is 

 by no means proved that the oldest Vertebrates 

 did not possess gastric glands, and that those 

 cases among fishes where they are absent are to 

 be explained through degeneration. The ab- 

 sence of the glands in these forms is thus wholly 

 a secondary modification, as is well shown by 

 the fact that the near relatives of those species 

 in which the glands are absent often possess 

 them in well-developed form. The glands have 

 arisen, not by a deepening and narrowing of the 

 folds of the mucous membrane, but as inde- 

 pendent invaginations starting from a very 

 limited area. The absence of gastric glands 

 among the Monotremes, where the whole 

 stomach is lined with a stratified epithelium 

 like that of the oesophagus, is due to secondary 

 changes, the oesophageal epithelium having 

 gradually grown down and displaced the 

 original gastric epithelium. 



An exhaustive discussion of the physiology 

 of the mammalian gastric gland-cells is given, 

 and the variety of views held by difierent 

 authorities shows very clearly the difiiculty 



