April 7, 1910] 



NATURE 



153 



present. But Prof. Eisen hart's work will be accept- 

 able to those who prefer English to other tongues, or 

 who wish to have the mail, results in a more con- 

 densed form than that in whicn Darboux and Bianchi 

 present them. 



The author of this book has been remarkably suc- 

 cessful in giving a large amount of matter without an 

 appearance of stodginess. The main reason for this 

 is that, besides having a crisp style, he is ven'- 

 judicious in omitting those links of connecting analysis 

 which the reader can easily supply for himself, or 

 take for granted as calculations which have been done 

 once for all. Without any attempt to enumerate even 

 all the principal topics discussed, it may be said that 

 we have a sufficient account of curvilinear coordinates, 

 conformal and other representations, differential para- 

 meters, and the Christoffel (or Riemann) symbols; 

 chapters on the deformation of surfaces, including 

 Minding's problem, and the method of Weingarten ; a 

 very compact account of geodesies, minimal and other 

 special surfaces; and finally chapters on rectilinear 

 congruences, cyclic systems, and triply orthogonal 

 systems of surfaces. Incidentally, many elegant 

 special applications are given ; thus, for instance, 

 there are several interesting theorems due to Bonnet. 



One remark is almost sure to occur to the reader 

 of the book, namely, that the use of the differential 

 parameters of the linear element is, in some parts of 

 the theory, a very powerful engine, at any rate, for 

 purposes of condensation and lucidity. An instance of 

 this will be found in the chapter on geodesies (pp. 

 ^15-8). No serious student of differential geometry 

 can fail to read Gauss's famous memoir and the early 

 papers by Lagrange and others on minimal surfaces; 

 few things are more instructive than a comparison of 

 these " path-breaking " memoirs with the compact and 

 symmetrical methods of the present day. The contrast 

 IS so great that the student who hopes to do something 

 himself is more than ever bound to read original 

 papers besides text-books and treatises ; otherwise he 

 ■will be tempted to imagine that new results fall out 

 of the sky, so to speak, in their final and clearest 

 and most elegant shape. 



Fortunately Prof. Eisenhart's book contains a 

 partial antidote in the shaf)e of a very useful collec- 

 tion of unsolved examples. These are of all grades of 

 difficulty, ranging from simple corollaries to adjacent 

 bookwork to important theorems extracted from 

 original papers. It would, perhaps, have been a help 

 in these latter cases to give a reference ; but the 

 author has been sparing in his bibliography, as indeed 

 mathematical writers can now afford to be, when the 

 " Encyclopaedie d. Math. Wiss." and the Royal 

 Society's " Subject Index " are available. 



In conclusion, a word on notation may be per- 

 mitted. The Christoffel symbols are so essential in 

 some parts of the theory that they ought to be of a 

 simpler character than they are; for instance, the 

 formulae on p. 155 may, in a sense, be expressive, but 

 they are cumbrous and ugly in the extreme. Could 

 not the Mathematical Congress, or some other body, 

 suggest a simplified notation, with some chance of 

 its being generally adopted? G. B. M. 



NO. 2 1 10, VOL. 83] 



THE INSPECTION OF FOOD. 

 Food Inspection. By Hugh A. Macewen. Pp. viii + 

 256. (London : Blackie and Son, Ltd., 1909.) 

 Price 55. net. 



T^HIS work has been written with the object of 

 -■- giving a clear and concise account of the inspec- 

 tion of meat and other foods, and of the principles 

 underlying the hygienic production of prepared foods. 

 It embodies the author's personal experience of the 

 methods employed in Berlin and other German towns, 

 America, and Great Britain. The book, which is 

 well illustrated, includes chapters upon meat inspec- 

 tion ; the inspection of live animals, and the symp- 

 toms of the more important diseases from which they 

 suffer; the methods of slaughter; the diseases com- 

 monly met with in the abattoir; the construction and 

 management of slaughter-houses and abattoirs ; the 

 inspection of fish, poultr}-, game, fruit, and vegetables ; 

 the preservation and storage of food ; the inspection 

 of prepared foods ; and the law relating to the above 

 subjects. In the anatomical description given the ox 

 is taken as the type, and whenever any of its organs 

 or parts differ markedly from those of other animals 

 which concern the meat inspector, a special descrip- 

 tion is given. Important anatomical facts include a 

 clear statement and good illustrations of the situation 

 of the principal lymphatic glands in cattle and pigs. 



An interesting and useful appendix deals with the 

 German method of meat inspection as carried out in 

 Berlin, and another appendix furnishes a short 

 description of Chicago stockyards and packing- 

 houses, and of American methods of meat inspection. 

 The writer condemns the private slaughter-house 

 which is so general in this countr}-. If inspection is 

 to be efficient it is essential that the inspector should 

 be present while the slaughtering is going on. This 

 is impossible in all the private slaughter-houses ; and 

 therefore no adequate system of meat inspection is 

 possible where they are suffered to exist. The organs 

 of unsound animals may be concealed or destroyed 

 before the inspector appears on the scene, and the 

 writer testifies to the fact that there is often a 

 marked want of cleanliness in the methods of dress- 

 ing and preparing the meat in private slaughter- 

 houses, which is not to be witnessed in public abat- 

 toirs. 



The w-ork will not serve as a reference book. The 

 information offered is not comprehensive enough for 

 that purp>ose ; but it is admirably designed to provide 

 what the average food inspector and public-health 

 student requires from a text-book. In parts the 

 matter will be judged by the medical reader as very 

 elementar}-, but the book has been written mainly to 

 meet the needs of non-medical readers ; the former, 

 however, will find a ver\- great deal to interest and 

 instruct. Indeed, it may be read with profit by all 

 who are interested in the public food supply, and it 

 will probably prove to be the most serviceable text- 

 book which candidates preparing for the examinations 

 for the food inspector's certificate, granted by the 

 Royal Sanitary Institute and other bodies, may con- 

 sult. Both in respect of the matter it contains and 



