March 24, 1881] 



NATURE 



481 



In a book however intended for medical students, it is, 

 in our opinion at least, of the utmost importance that the 

 facts of embryology should not merely be stated in suc- 

 cession, but that their significance should be pointed out. 

 Embryology is of but little practical value to a medical 

 student, and the small amount he must necessarily know 

 could be given in a very few pages, and is, we believe, 

 usually to be found in works on human anatomy. Con- 

 sidered however as an educational instrument, embryology 

 is of the utmost value. It gives to the student an insight 

 into the meaning of the structures which he meets with 

 in his dissections, and by so doing often renders details 

 of anatomical structure comparatively easy and pleasant 

 of acquisition, which would otherwise be a great and 

 almost repulsive strain on the memory. 



Embryology should be taught to the medical student as 

 a comparative science ; with the facts duly marshalled) 

 their significance pointed out, and general principles 

 deduced from them. In such a form it ought to constitute 

 an important part of medical training, which every medical 

 school of any pretence to excellence should impart to its 

 students. 



We -would venture to call attention to the following 

 instances as illustrative of what we consider the unsatis- 

 factory treatment of certain parts of the subject to be 

 found in Prof. Kolliker's work. In dealing with the 

 phenomena of segmentation Prof KoUiker makes no 

 effort to point out that the difterences in the early deve- 

 lopment of the mammal and bird are in the main the 

 result of the presence of food yolk in the one case and its 

 absence in the other. After reading his very careful and 

 elaborate treatment of the primitive streak, the student 

 would, we think, be left in complete ignorance of the real 

 significance of this interesting structure. 



Again, in his account of the placenta, which he describes 

 in man and the rabbit, he has so little to say as to any 

 comparison between the two that we are at a complece 

 loss to understand why he should have made any mention 

 of the former. 



In his account of the development of the vascular and 

 excretory systems we are struck with the almost entire 

 lack of any attempt to put the facts which have been so 

 admirably described to their legitimate use, viz. to the 

 explanation of the arrangement of these and other struc- 

 tures in the human body, and of the presence of rudi- 

 mentary organs. 



In making these strictures on Prof Kolliker's work we 

 should be sorry to convey the impression that we under- 

 estimate the value of this in most respects admirable 

 treatise. It has already become justly popular in Germany, 

 and we trust that it will also become widely known in this 

 country. 



OUR BOOK SHELF 



Bulletin of the United States Geological and Geographical 

 Survey of the Territories, 1879-S0. Vol. v. (Wash- 

 ington, 1880.) 

 The publications issued by the American Government 

 under the above title are so appreciated in this country 

 that it seems unnecessary to compliment Dr. Hayden 

 and his coadjutors on the appearance of another of their 

 useful volumes. During the last few years, however, there 

 have been brought out by the U.S. Department of the 

 Interior some works by Dr. Elliot Coues, which for 



patient industry must compare with any that have ever 

 been compiled in scientific literature. The title of the 

 volume now before us reads as follows : — .Art. 26. Third 

 Instalment of American Ornithological Bibliography, by 

 Dr. Elliot Coues, U.S.A., and consists of 545 octavo 

 pages of small print. How many titles of papers and 

 books are i-|uoted in this laborious treatise we should be 

 sorry to have to count. The labour must have been 

 enormous, and it is only those who have to follow the 

 intricate windings of synonymic literature who can appre- 

 ciate the work here performed by Dr. Coues. We learn 

 that we may expect at some future time a similar con- 

 spectus of titles relating to the ornithology of the Old 

 World, but although the present volume professedly 

 deals with American Birds only, many standard works of 

 general interest are passed in review by the author, who 

 exhibits great judgment as a critic. Taking Gray's 

 "Hand-List of Birds" as a basis of classification to 

 follow, Dr. Coues treats of each family separately, and 

 then in chronological order he records evei-y work, every 

 paper, and every note which directly or indirectly affects 

 the American species, and as regards each year the publi- 

 cations are separately entered under the authors' names in 

 alphabetical order. We must however again warn orni- 

 thologists that so many collateral references are given to 

 Old World papers where the families are at all cosmo- 

 pohtan, that therefore no one writing on any group of 

 birds can aflbrd to neglect this book. As for Dr. Coues 

 himself, we can only imagine the sigh of relief with which 

 he must have corrected the last proof of such a toilsome 

 undertaking, although he must have been assured before- 

 hand of the heartfelt gratitude of every ornithological 

 confrere throughout the globe. R. B. S. 



(i.) Exposition Geoinetriqiie des Proprietes generates des 



Courbes. Par Charles Ruchonnet (de Lausanne). 



Quatrieme (fdition augmentde. (Paris, 1880.) 

 (ii.) Elements de Calciil approximatif. Par C. Ruchonnet 



(de Lausanne). Troisilme edition revue. (Paris, 1880.) 

 Having noticed both these works on the appearance of 

 the last previous editions in 1874, we need say little here. 

 The reasoniiv,; in i., we may remark, is always upon the 

 curve itself, and is not derived by taking the limiting form 

 of the inscribed polygon ; and similarly in the case of 

 surfaces. The work has grown from 160 pp. to 174pp., 

 and there is one more plate of figures. 



The pamphlet ii. is, what it is stated to be, a revised 

 form of the last edition. It consists of 64 pp. in place of 

 65 pp. 



Geschichte der geographischen Entdeckungsrcisen im 

 Alterthum und Mittelalter. Von J. Lowenberg. (Leip- 

 zig und Berlin : Otto Spamer, 1881.) 

 This is a volume in the publisher's Illustrated Library of 

 Geography and Ethnology. It is, as its title indicates, 

 a Historj' of Geographical Discovery in Antiquity and 

 during the Middle Ages. The story is brought down 

 to the time of Magellan and Martin Behaim. The 

 first book, under the heading of Night and Morning, 

 treats of the earliest dawn of geographical knowledge 

 with the Hebrews, Egyptians, Babylonians, Phcenicians, 

 Greeks, and Romans ; the second book embraces the 

 period from Herodotus to Ptolemy ; the third, the Middle 

 Ages ; and the fourth the Century of Discovery, in which 

 Spain and Portugal did such splendid work. Herr Lowen- 

 berg has evidently taken great pains to master his subject, 

 and has been quite successful. He treats it in consider- 

 able detail, both in its historical and scientific aspects ; 

 the arrangement is excellent, and while popular and at- 

 tractive in style, the work seems to us to be accurate and 

 altogether trustworthy. There are numerous illustrations, 

 some of them rather fanciful, but most of them useful and 

 appropriate—portraits, ships of various periods, maps, 

 some of them reproductions of very early ones, and 



