Od. 29, 18:^4] 



NATURE 



S19 



to cut the air so as to meet with the minimum of resist- 

 ance ; while in its descent, on the contrary, the position 

 of its plane is reversed, so that its lower surface turns 

 downwards and slightly backwards." During the descent 



of the wing the body of the bird is carried forwards as 

 well as upwards. The resistance of the air explains the 

 elliptical form of the figure. 



We hope that in the short glance which we have taken 

 of some of the most important pomts discussed in the 

 work before us, we have succeeded in interesting our 

 readers sufficiently in its contents to make them curious 

 to learn more of its subject matter. We cordially recom- 

 mend it to their attention. To the student of art it gives 

 rules and general principles which will be found invalu- 

 able in all attempts to portray the various attitudes of 

 man and his faithful companion, the horse ; and these, 

 when understood, will direct attention to the most salient 

 points in the locomotion of other animals. 



To the student of physiology it is useful in at least two 

 ways. It shows how invaluable is a knowledge of mani- 

 pulatory details and the principles of mechanics. Prof. 

 Marey, in the period of his studentship, must have learnt 

 more than the simple routine facts of a medical education. 

 The mechanical Cardan universal joint and Whcatstone's 

 kaleidophone rod are as familiar to him as is the valvular 

 mechanism of the heart ; it is his control of method which 

 is one of his most marked characteristics. It shows how 

 elaborate are some of the phenomena which at first sight 

 seem so simple, and how much the science of physiology 

 is within the domain of physics. 



The translation, as far as we have had the opportunity 

 of judging, seems a good one, e.\cept in one or two cases, 

 where improvement would not be impossible. 



OUR BOOK SHELF 



The Protoplasmic Theory of Life. By John Drysdale, 

 M.D. (Bailliere, Tyndall, and Co.x, 1S74.) 



THE author of this small book is one of the editors of a 

 work on Pathology, by Dr. John Fletcher, of Edinburgh, 

 whose " Rudiments of Physiology " contains much specu- 

 lative biology of no mean quality. As a disciple he 

 enters into an analysis of the philosophy of his master, 

 discussing its details in connection with the light thrown 

 upon it by modern research, especially the bioplasm 

 theory of Beale. Fletcher argued thus :— The peculiar j 

 property, vitality, does not reside in the tissues of the 

 living body indiscriminately, but in one anatomical 

 element alone ; because, as the various tissues differ 



extremely in their physical properties, and these latter 

 are almost exactly the same after as before death, it is 

 hardly to be expected that the living matter can rearrange 

 itself on death, in a short time, into a number of different 

 forms, which shall possess exactly the same physical 

 properties in the vital as in the ordinary state of combi- 

 nation. The concordance of this idea with the theory of 

 Dr. Beale, which divides all tissues into a living forming 

 material (bioplasm), and a dead formed material, the com- 

 position of the latter of which alone varies to any extent, 

 must be evident to all ; and the wo rking out of its minutiit; 

 occupies several chapters of the work before us. The 

 author also enters fully into the muscle and nerve theory of 

 Dr. Beale in a manner which we do not think will throw 

 much light on cither subject. He remarks that the insu- 

 lating power of the medullary sheath of the nerve-fibre 

 is not demonstrable, therefore " the nerves are not fitted 

 for simple conduction of electric currents ; and these have 

 no reason to choose the nerves as their channels, so they 

 spread through the moist tissues almost uniformly." With 

 this opinion we think there are few or no physiologists 

 who will agree, as there is not the least doubt that it is 

 through nerve-fibres that electric stimulation will most 

 readily and most powerfully affect muscular fibres at a 

 distance ; otherwise, what is the peculiar value of the 

 " nerve-muscle preparation " of the physiological labora- 

 tory .? In his remark that Dr. Sanderson is premature 

 in arguing with regard to the Dion.^"a "that because the 

 contraction of the plant-leaf depends on changes, appa- 

 rently in the contents of the cells, the muscular contrac- 

 tion of the higher animals is of the same nature," the 

 author is, we think, more fortunate ; we have never been 

 able to see that the two phenomena have anything in 

 common. From the consideration of the less speculative 

 protoplasmic theory of the origin of tissues, such points as 

 the nature of life, the connection of force with life and 

 mind, consciousness, and materialism, subjects beyond 

 the pale of precise knowledge, are treated of in a manner 

 which will quite repay perusal by those who are fond of 

 speculating on those precarious topics. 



Out of Doors : a Seiection of Original Articles on Prac- 

 tical Natural History. By the Rev. J. G. Wood, M.A., 

 F.L.S. (London: Longmans and Co., 1874.) 



Mr. Wood is well known as one of the most suc- 

 cessful popularisers of natural history. He has him- 

 self an extensive and thorough knowledge of his subject, 

 as well as a genuine love of it, and his genial enthusiasm 

 cannot fail to infect the minds of the fortunate boys and 

 girls into whose hands his books may fall. The present 

 volume consists of a number of thoroughly readable 

 papers which have already appeared in various periodi- 

 cals. They are written in an easy, graceful, chatty style ; 

 and while apparently trying only to amuse his readers, 

 he manages to convey a great deal of valuable informa- 

 tion about animals and plants, especially about such 

 as anyone who likes to take the trouble may observe 

 for himself. Some of the papers are concerned with 

 exotic animals, as in that describing " A January Day 

 at Regent's Park," in which are contained many facts 

 concerning the inhabitants of the Zoological Gardens. 

 Most of them are, however, about the " common objects 

 of the country," as is indicated by such titles as " A Sand 

 Quarry in Winter," " Under the Bark," " My Toads," 

 "The Children of the New Forest," "The Repose of 

 Nature," the last concerned with hybernating animals. I n 

 " Medusa and her Locks," and " Life on the Ocean Wave " 

 (describing a visit to the Crystal Palace Aquarium), " The 

 Green Crab," &c., we are introduced to the denizens of 

 the ocean. The book is an excellent one to give to a 

 boy or a girl, who, we are sure, would enjoy it, as indeed 

 would many whose boyhood or girlhood is only a sad 

 memory. 



