8o 



NATURE 



[May 31, 1877 



great veins which open into the heart. And there is no 

 doubt that Dr. Foster is right in describing this as a 

 distinct factor in the cardiac cycle. 



The manner in which the nervous system is introduced 

 to the student calls for special comment. In treating of 

 the various phenomena of the circulation, respiration, 

 secretion, &c„ frequent mention must necessarily be 

 made of the relation of the nervous system to those func- 

 tions. This pre-supposes a knowledge of the mode of 

 origination and transmission of nervous impulses, and of 

 the changes they may undergo in transmission, and 

 hence of the fundamental properties of the nervous tissues. 

 It might well, therefore, be deemed proper to commence a 

 work on physiology with the account of a system which, 

 in the higher animals at least, dominates and directs all 

 the other functions. But on the other hand, from its 

 greater intricacy, it is found in the teaching of physio- 

 logy by far the most convenient plan to defer the account 

 of the nervous system until the simpler, and more ob- 

 viously physical phenomena of the living body have been 

 dealt with. 



Dr. Foster has got out of the dilemma in an ingenious 

 and effectual manner. For whilst the account of the 

 central nervous system and its principal instruments — 

 the sense-organs — are reserved for one of the concluding 

 chapters of the book, a short exposition of the funda- 

 mental properties of the nervous tissues, and also, but in 

 very general terms, of the special functions of the chief 

 nervous centres, is introduced at quite an early stage — a 

 mode of dealing with the subject which enables such im- 

 portant questions as the influence of the nervous system 

 upon the heart, respiration, secretion, &c., to be discussed 

 at length with their respective subjects in place of being 

 deferred until the end of the book. We are not sure that 

 this introduction to the nervous system might not with 

 advantage have come in even earlier than it does ; as a 

 sequel, in fact, to the chapter with which the work is 

 introduced. 



We quote a few passages from the prefatory article 

 on the fundamental properties of the nervous^system as 

 yielding an illustration of the gradual, easy way in which 

 Dr. Foster leads up to a difficult subject : — 



" In its simplest and probably earliest form a nerve is 

 nothing more than a thin strand of irritable protoplasm, 

 forming the means of vital communication between a 

 sensitive ectodermic cell exposed to extrinsic accidents, 

 and a muscular, highly contractile cell (or a muscular 

 process of the same cell) buried at some distance from 

 the surface of the body, and thus less susceptible to 

 external influences. If in hydra we imagine the junction 

 of the ectodermic process with the body of its cell to be 

 drawn out into a thin thread (as appears to be the case in 

 some other hydrozoa), we should have just such a primary 

 nerve. Since there would be no need for such a means 

 of communication to be contractile and capable of itself 

 changing in form, but on the other hand an advantage in 

 its remaining immobile, and in its dimensions being 

 reduced as much as possible consistent with the main- 

 tenance of irritability, the primary nerve would in the 

 process of development lose the property of contractility 

 in proportion as it became more irritable, z>., more apt 

 in the propagation of the waves of disturbance arising 

 within the ectodermic cell. 



" We have already seen (introductory chapter) that 

 automatism, /.<■., the power of initiating disturbances or 

 vital impulses, independent of any immediate disturbing 



event or stimulus from without, is one of the fundamental 

 properties of protoplasm. In simpler but less exact 

 language, such a mass of protoplasm as an amceba, 

 though susceptible in the highest degree to influences 

 from without, 'has a will of its own.' .... A hydra has 

 also a will of its own ; and seeing that all the constituent 

 cells are alike, we have no reason for thinking that the 

 will resides in one cell more than in another. ... In 

 both hydra and amceba the processes concerned in auto- 

 matic or spontaneous impulses, though in origin indepen- 

 dent of, are subject to and largely modified by, influences 

 proceeding from without .... 



"The next step of development beyond hydra is evi- 

 dently to differentiate the single (ectodermic) cell into 

 two cells, of which one, by division of labour, confines 

 itself chiefly to the simple development of impulses as 

 the result of stimulation, leaving to the other the task of 

 automatic action, and the more complex transformatioa 

 of the impulses generated in itself The latter, which we 

 may call the eminently automatic cell, will naturally be 

 withdrawn from the surface of the body, while the other, 

 which we may call the eminently sensitive cell, will still 

 retain its superficial position, so that it may most readily 

 be afi'ected by all changes in the world without. And j jst 

 as a primary motor nerve arises as a retained thread of 

 communication between a sensitive cell and its own muscu- 

 lar process, so a primary sensory nerve may be conceived 

 of as arising as a thread of communication between an 

 eminently sensitive cell, and its twin the eminently auto- 

 matic cell Naturally the muscular process or mus- 

 cular fibre would, on the splitting of the original single 

 cell, remain in connection with the most eminently 

 automatic. We thus arrive at that triple fundamental 

 arrangement of a nervous system in its simplest form, 

 viz., a sensitive cell on the surface of the body connected 

 by means of a sensory nerve with the internal automatic 

 central nervous cell, which in turn is connected by means 

 of a motor nerve with the muscular fibre-cell " 



In the introductory chapter of the book the physio- 

 logical processes which occur in the amoeba arc described, 

 and these are taken as the basis upon v/hich the whole 

 superstructure of the science is to be built up. This is a 

 wise course to pursue, for in a work on physiology the 

 amceba cannot have too prominent a place assigned to it. 

 It is over the amreba that the batde of physiology must 

 eventually be fought out. 



The chief organic compounds met with in the animil 

 body are considered together in an appendix, which has 

 evidently been carefully drawn up, and will be found not 

 the least useful portion of the book. It is, no doubt, an 

 advantage in many respects to have a series of similar 

 facts thus collected and put on one side for reference. At 

 the same time it may be questioned whether in the case 

 of some of the bodies which hive been relegated to this 

 situation — the constituents of the blood and urine, for 

 example — it would not have been better rather to have 

 awarded them somewhat greater prominence in the parts 

 of the book which treat of the special fluids or secretions 

 in which they occur. A frequent reference to the appendix 

 in such places might answer the purpose. 



It is pleasant in a book of this sort to be able to find 

 so little that is open to adverse criticism. It is true the 

 latter part of the work bears traces of haste, and one or 

 two important subjects are somewhat lightly dealt with. 

 Moreover here and there statements which are anything 

 but " fixed and sure " are to be found clothed in large 

 type, while others, which are based upon a large number 

 of exact experiments (the observations of Ludwig and 



