818 



SCIENCE. 



[N. S. Vol. XVII. No. 438. 



illustrations; a number of fine figures are 

 transferred from the original sources to a 

 text-book for the first time, and only the 

 best of the stock illustrations of other test- 

 books are retained. The book is, indeed, built 

 up around the illustrations, and the text often 

 suffers by comparison. The figures of recon- 

 structions of the pig embryo of twelve milli- 

 meters neck-length are especially fine, as are 

 also the figures of sections of this embryo and 

 of other sizes. In all of these figures there is 

 the most painstaking reproduction of details, 

 and the accuracy of the work, is equaled only 

 by its beauty. The illustrations of the two 

 stages of the chick embryo studied are also 

 noteworthy for accuracy and finish. 



The contents are arranged as follows: The 

 first chapter deals with general conceptions, 

 the second with the early development of 

 mammals, and the third with the most general 

 development of the human embryo. These 

 chapters are introductory in their scope, with- 

 out practical directions. The following chap- 

 ters are practical; the fourth deals with pig 

 embryos : beginning with the embryo of 12 

 mm., there follow in order, embryos of 9 mm., 

 6 mm., 17 mm. and 20 mm. The fifth chapter 

 is a study of two stages of the embryo chick, 

 with twenty-four somites, and with seven 

 somites. In chapter six we have a study of 

 the blastodermic vesicle of mammalia and of 

 the segmentation of the ovum.. Chapter seven 

 deals with the uterus and the fcetal append- 

 ages of man, and chapter eight with methods. 



Thus it will be observed that the student 

 is led from a 12-mm. pig to a 9-mm. and, 

 fi-mm. stage, then by jumps to 20-mm. ; from 

 here a broad leap takes him to the youngest 

 embryo yet studied, the chick of twenty-four 

 somites, and he continues to descend by way 

 of earlier stages of the rabbit, to the imseg- 

 mented ovum. This may fairly be termed 

 inverted embryology. Professor Minot wiU 

 not claim that this inverted order is logical, 

 but only that is practical. It is a question of 

 the pedagogy of embryology. Now it is safe 

 to admit, that, for an anatomist who knows 

 nothing of biology, the inverted method of 

 studying embryology is likely to be the more 

 comprehensible; and as most of our medical 



students are (crude) anatomists of this sort, 

 it may be that their journey to embryological 

 knowledge would subject them to fewer intel- 

 lectual jolts if made by this road. It cer- 

 tainly is the historical highway by which the 

 fathers of this science traveled; if recapitu- 

 lation be the law in embryonic development, 

 why not in embryological pedagogics? 



It seems to me, however, to be an unwise 

 concession to the present imperfect preparation 

 of our medical students, and, in all seriousness, 

 I believe an unnecessary concession; for my 

 experience is that, after the first shock of ex- 

 posure to biological conception and ideas, the 

 medical student readily follows the coenogen- 

 etic and logical method of proceeding up- 

 wards from the ovum. Moreover, the time 

 is not far distant when every medical student 

 will be required to have mastered the rudi- 

 ments of biology before he shall be admitted 

 to the study of that branch of applied biology 

 known as medicine. With such a preparation 

 the logical method is much better. 



It is not, however, incumbent on the user 

 to follow the order of the book, for the de- 

 scription of each stage is complete in itself. 

 Those who use it, therefore, will probably fol- 

 low their own ideas of order; and the prac- 

 tical parts can be unhesitatingly recommended 

 as excellent in themselves. 



The chapter on methods is rather brief, but 

 good as far as it goes; a larger number of 

 formulse of killing fluids and stains and the 

 methods of using them would undoubtedly be 

 an improvement. 



The three general introductory chapters are 

 best, as is to be anticipated, in the parts allied 

 to the author's own province of work; thus 

 the ' law of genetic restriction ' is well ex- 

 pressed and discussed; and the third chapter 

 on the human embryo is by far the best brief 

 outline of human development knovm to me. 

 On the other hand, the unfortunate student 

 who might have to derive his ideas on karyo- 

 kinesis and on the maturation of the ovum 

 from the vague accounts of this book, would 

 probably conclude, for his own peace of mind, 

 that these subjects are not of much importance 

 after all. As regards the germ-layers in mam- 

 mals we read on p. 59 that ' it is probable that 



