Page:Popular Science Monthly Volume 42.djvu/729

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usual term of segmentation of the ovum, even though he has the precedence afforded by Prof. Huxley's employment of a term that should have been left to its original scientific use in geology and mineralogy.

The methods of development of the two primary and of the two middle germ layers—the so-called gastræa theory and cœlom theory—are presented in separate chapters. The author maintains that at the close of segmentation there is only one germ layer present—the epithelium of the blastula. From it the remaining germ layers arise by the processes of invagination and evagination—the inner germ layer being formed by means of gastrulation, the two middle germ layers being formed by the formation of the body cavities, in that two body sacs are evaginated from the cœlenteron and grow out between and separate the two primary germ layers. After their origin the middle germ layers are differentiated into several fundaments (rudiments) by processes of folding and constricting off.

The development of the connective substance and blood is explained by means of the mesenchyme germs. This is followed by chapters on the establishment of the external form of the body and on the fœtal membranes of reptiles, birds, mammals, and man.

The consideration of the science of the embryology of organs is divided into four sections, comprising the morphological products of the inner, of the middle, of the outer, and of the intermediate germ layers. This is, of course, an arbitrary division, for the teeth arise from the intermediate and the outer germ layers, while the alimentary canal and its glands contain elements from the inner, middle, and intermediate layers.

Space forbids any extended consideration of the features pertaining to these latter topics. The work is certainly a comprehensive presentation of the subject, and the translator has performed his arduous task in a satisfactory manner.

Commercial Organic Analysis. By Alfred H. Allen. Volume III, Part II. Philadelphia: P. Blakiston, Son & Co. Pp. 584. Price, $5.

Each successive portion of this valuable work testifies to the masterly ability with which its author has handled a large and difficult undertaking. The present part deals with Amines and Ammonium Bases, Hydrazines, Bases from Tar, and Vegetable Alkaloids. The substances of chief commercial importance that are treated are, therefore, drugs, such as aconitine, atropine, cocaine, morphine, quinine, and their allies; the alkaloids of coffee, tea, and cocoa, and the aniline colors. Substances of special interest at the present time which fall within the scope of this part are antipyrine and certain other antipyretics. A third part of Volume III is to be issued to complete the treatise, and it is gratifying to note that the success of the work in its enlarged form warrants the author in announcing a new edition of the earlier volumes.

Railway Injuries, with Special Reference to those of the Back and Nervous System, in their Medico-legal and Clinical Aspects. By Herbert W. Page. New York: William Wood & Co. Pp. 157.

The aim of this book is to give an account of the injuries received in railway and similar accidents that become the subject of medico-legal inquiry. The author has long been a student of this branch, having published in 1883 a work on Injuries of the Spine and Spinal Cord and Nervous Shock, to which he had given several years of preparation, and having continued his observations since. While injuries of all kinds and degrees are caused by railway accidents, they do not differ for the most part from those which are seen after other forms of violence. Even the injuries in the back received in railway accidents do not differ from similar injuries received in other ways; but their frequency, and the character they impress on the features of many other forms of injury, demand for them a place by themselves. It is, in fact, a peculiarity of railway accidents that these injuries of the back are nearly always produced, whatever other injuries may occur, and even though there may not be other injury; that the patient is often not aware of them till some time afterward, and that their direct and indirect effects are often widespread and long continued. Vastly more numerous and even more important than these are the cases of "general nervous shock"—an unprecise term applicable rather to the whole of the clinical circumstances of