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NA TURE 



\yan. 23, 1890 



as the foundation of that side of medical and surgical 

 practice which is based on a sound knowledge of regional 

 anatomy. The incomplete recognition of the physio- 

 logical aspect of anatomy is, we think, the weak part of 

 the book, and it is especially shown in the scanty notice 

 which is taken of the action of the muscles and their 

 association with the movements of the joints. 



To enable both these lines of anatomical study to be 

 pursued, the student is accustomed to employ at least 

 two text-books ; the one in connection with his syste- 

 matic work, the other as a guide to the dissection of the 

 body. Prof. Macalister apparently expects, as, indeed, 

 he states in his preface, that his text-book should stand 

 in the place of the two customarily employed. We doubt, 

 however, whether this expectation will be fulfilled. For his 

 text-book, in addition to what is essential in topographical 

 description, by containing an account of the microscopic 

 structure of tissues and organs, a section on embryology, 

 and a detailed description of the bones, is necessarily a 

 work of considerable size and weight, and too cumber- 

 some to be conveniently carried to and fro by the student, 

 as is required with a dissecting-room manual. On the 

 whole, therefore, we prefer the old and well-accustomed 

 lines on which text-books have for so long been written, 

 to Prof. Macalister's modified plan. 



But whilst expressing our inability to regard the method 

 which has been followed in the descriptive anatomy of 

 the soft parts as an improvement on the customary 

 arrangement of systematic text-books, we recognize with 

 pleasure the clearness of the descriptions and the many 

 suggestive hints, both morphological and practical, which 

 the book contains. The volume is profusely illustrated 

 with upwards of eight hundred wood-cuts, about one half 

 of which are original figures. 



OUR BOOK SHELF. 



A Treatise on Ordinary and Partial Differential Equa- 

 tions. By W. W. Johnson. (London: Macmillan, 

 1889.) 



We have read Prof. Woolsey Johnson's work with some 

 interest : his style is clear, and the worked-out examples 

 well adapted to elucidate the points the writer wishes to 

 bring out. He appears to recognize Boole, but, so far as 

 the text is concerned, does not acknowledge the existence 

 of Mr. Forsyth's fine work. We do not say that he was 

 under any obligation to do so, but nowadays we are so 

 accustomed to see a list of authors upon whom a writer 

 has drawn that we missed it here. " An amount of space 

 somewhat greater than usual has been devoted to the 

 geometrical illustrations which arise when the variables 

 are regarded as the rectangular co-ordinates of a point. 

 This has been done in the belief that the conceptions 

 pecuhar to the subject are more readily grasped when 

 embodied in their geometric representations. In this 

 connection the subject of singular solutions of ordinary 

 differential equations, and the conception of the character- 

 istic in partial differential equations may be particularly 

 mentioned." This is certainly the most prominent feature 

 of the early chapters, and it is, to our mind, clearly put 

 before the student. Reference is duly made to Prof. 

 Cayley's work in the Messenger of Mathematics (vol. ii.), 

 which initiated the present mode of treatment of the sub- 

 ject, but not to Dr. Glaisher's "Illustrative Examples" 

 (vol. xii.), nor to Prof. M. J. M. Hill's paper (London 

 Math. Soc. Proc, vol. xix.), in which the theorems stated 

 by Prof. Cayley are proved. This paper, though read 

 before the Society, June 14, 1888, may not have reached 



the author before his work was in the printer's hands : we 

 do not say that a perusal of it would have called for any 

 further notice than a reference. Symbolic methods come 

 in for their due meed of recognition and employment. The 

 author satisfies himself with referring the student to the 

 table of contents for the topics included and the order 

 pursued in treating them. The work consists of twelve 

 chapters divided up into twenty-four sections : i. (i) dis- 

 cusses the nature and meaning of a differential equation 

 between two variables ; ii. (2, 3, 4,) equations of the first 

 order and degree ; iii. equations of the first order, but not 

 of the first degree, (5) singular solutions (discriminant, 

 cusp-, tac-, and node-loci), (6) Clairaut's equation, (7) 

 geometrical applications, orthogonal trajectories ; iv. (8) 

 equations of the second order ; v. (9, 10) linear equations 

 with constant coefficients, in (10) symbolic methods are 

 employed; vi. (11-13) linear equations with variable co- 

 efficients ; vii. (14, 15) solutions in series; viii. (16) the 

 hypergeometric series ; ix. (17) special forms of differential 

 equations, as Riccati's equation (due reference is made to 

 Dr. Glaisher's classical paper in the Phil. Trans, for 1881), 

 Bessel's equation, and Legendre's equation (reference is 

 made to text-books and memoirs) ; x. (18-20) equations 

 involving more than two variables ; xi. (21, 22) partial differ- 

 ential equations of the first order ; xii. (23, 24) partial differ- 

 ential equations of higher order. Examples for practice are 

 added at the end of each section. Though Prof. Johnson 

 cannot lay claim to have made here any additions to our 

 knowledge of the subject, he has produced an excellent 

 introductory hand-book for students, and this, we expect, 

 was the object he proposed to himself in its compilation. 

 We have omitted to state that all use of the complex 

 variable is eschewed. 



The Land of an African Sultan : Travels in Morocco^ 

 1887,1888, a«^i889. By Walter B. Harris, F.R.G.S- 

 (London: Sampson Low and Co., 1889.) 

 A GOOD deal has been written about Morocco lately, 

 and Mr. Harris's volume is an interesting, although not a 

 very important, contribution to the literature of the subject. 

 He describes first a journey through northern Morocco, 

 then a journey with H.B.M. Special Mission to the court 

 of the Sultan at Morocco city, next a visit to Wazan and 

 a ride to Sheshuan ; and in a final chapter he sums up 

 the impressions produced upon him by the Moors and their 

 country. In the chapter on his ride to Sheshuan, he de- 

 scribes a place which had been " only once before looked 

 upon by Christian eyes." Mr. Harris does not pretend 

 to have produced an exhaustive work on Morocco ; but 

 he presents clearly what he himself has had opportunities 

 of observing. 



Wayside Sketches. By F. Edward Hulme, F.L.S., F.S.A. 



(London : Society for Promoting Christian Knowledge, 



1889.) 

 This is a pleasantly conversational book on all sorts of 

 subjects more or less connected with natural history or 

 country life : birds, caterpillars, flowers, snow-crystals, 

 and the forms of clouds, all come in for a share of atten- 

 tion. Without having any scientific pretensions of its 

 own, the book may well serve to rouse a first interest in 

 many branches of science. The numerous illustrations 

 are very good indeed. 



LETTERS TO THE EDITOR. 

 \The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of NATURE, 

 No notice is taken of anonymous communications. "{ 



Influenza. 

 The following paragraph, taken from Sir David Brewster's 

 "Life of Sir Isaac Newton," is not uninteresting at the present 

 time : — 



