50 



NA TURE 



[May 15, 1890 



increase in frequency can diminish impedance ; it always 

 tends to increase it ; and in no case can the impedance 

 of a conductor to alternating currents fall below that felt 

 by steady ones. Both resistance and impedance increase 

 with frequency. It is true that inductance diminishes, 

 but the diminution is very slight except for iron rods. 

 The punctuation of p. 353 has gone somewhat astray. 



All these are trifles : the average level of the book is 

 high, and it contains few dull pages. The practical im- 

 portance and interest of the subject treated is so great that 

 there should be little need to urge students and electrical 

 engineers to make themselves acquainted with it, but I do 

 urge them nevertheless ; and they may think it fortunate 

 that Dr. Fleming has managed to find time to issue so 

 instructive and readable and well-timed a volume. 



Oliver J. Lodge. 



McKENDRICK'S ''SPECIAL PHYSIOLOGY:' 

 Special Physiology, including Nutrition, Innervation, and 

 Reproduction. Vol. II. By J. G. McKendrick, M.D., 

 LL.D., F.R.S. (Glasgow: Maclehose and Sons. 

 London : Macmillan and Co. 1889.) 



IN the first volume the only purely physiological part 

 was that on muscle, leaving all the rest of the science 

 to be treated of in this volume, which thus includes the 

 physiology of digestion, nutrition, blood and circulation 

 respiration and the nervous system, as well as reproduc- 

 tion. It is evident that the book must either be of an 

 entirely elementary character, or that the treatment must 

 in parts be extremely inadequate, in order to include all 

 these subjects within the dimensions of a moderate-sized 

 volume. As a matter of fact, it lies open to both these 

 objections. In some places the author hampers himself 

 in the treatment of the purely physiological part of the 

 subject by expounding the first elements of chemistry and 

 physics (for the benefit, I suppose, of the average Glasgow 

 student) ; while other parts, though good, are much too 

 condensed to be understood by the reader who is ignorant 

 of the first principles of science. This disproportion in 

 the treatment of the various subjects meets us at the very 

 beginning of the volume, where twenty pages are de- 

 voted to dietetics before any description has been given 

 of the processes of digestion. 



In the section on digestion a very good condensed 

 account is given of the theory of secretion. One is sur- 

 prised, however, to meet with the statement that the sub- 

 maxillary ganglion can act as a reflex centre. The im- 

 portance of this view for the physiology of sporadic 

 ganglia is enormous ; yet Prof. McKendrick is content 

 with describing Claude Bernard's old experiments, which 

 seemed to support it, and makes no mention of the 

 researches of Bidder and Schiff, made so long ago as 

 1867, which showed that the secretion obtained in 

 Bernard's experiments was due to recurrent fibres of the 

 chorda tympani, and not to any action of the ganglion as 

 a reflex centre. 



The account of the action of the bile on the chyme is 

 not quite accurate. He says : " At the same time the 

 taurocholate of soda throws down the non-peptonized 

 albuminous matters, such as coagulable albumin and 

 syntonin, while the hemialbumose and peptones remain 

 in solution." As a matter of fact, the precipitate consists 



of parapeptone (syntonin) with a small quantity of 

 peptones. 



In describing the formed elements of the blood, no 

 mention is made of the plasma or granule cells. Yet 

 these are daily assuming a larger importance in patho- 

 logical processes, and every student who is to study 

 medicine should at any rate know of their existence. 



In the section on coagulation as fair an account is given 

 of Wooldridge's work on the subject as is possible in the 

 limits of a page and a half; but in his summing up of 

 the differences between this observer and Halliburton, he 

 does not seem to have grasped Wooldridge's theory. He 

 rejects this on the grounds that all Wooldridge's work was 

 done with peptone plasma (which was not the case), and 

 that fibrinogen (Hammarstens) contains no lecithin and 

 can yet clot on addition of lecithin free ferment. That 

 fibrinogen contains no lecithin is, to say the least, ex- 

 tremely doubtful. Bunge states that he has never suc- 

 ceeded in preparing any proteid free from phosphorus. 

 It is practically impossible, however, to form a good 

 judgment on the merits of Dr. Wooldridge's work without 

 reading al] his papers on the subject. In none of them 

 has he discussed the question in all its details, and it is 

 probably on this account that his work has been so mis- 

 understood and misrepresented. 



It is surprising how few books on physiology mention 

 the role of the spleen (made so much of by MetschnikofT) 

 as the great blood-filter, where all effete blood corpuscles 

 and other deleterious materials are devoured and de- 

 stroyed by the cells of the splenic pulp. In this volume 

 the rhythmic movements of this organ are fully described, 

 and a long list is given of the extractives that it contains, 

 but its function is left entirely in doubt. 



The next two sections, on the circulation and respira- 

 tion, present the subject fairly completely, and are brief 

 without being obscure. Yet these are not free from some 

 misleading statements. Thus the depressor nerve is 

 included among the afferent nerves that act on the inhi- 

 bitory or accelerating cardiac centres, so that a student 

 would imagine that stimulation of this nerve lowered the 

 blood-pressure by reflex inhibition of the heart — a mistake 

 one meets with only too often in teaching. Again, in 

 describing the forces concerned in tarrying on the cir- 

 culation through the capillaries, he makes the following 

 statement : — 



" Some have supposed that it is supplemented by an 

 attractive influence exerted by the tissues {vis a fronte), 

 and the statement is supported by the observation that, 

 when there is an increased demand for blood owing to 

 active nutritional changes, there is an increase in the 

 amount of blood flowing to the part, such as occurs, for 

 example, in the mammary gland during lactation, and in 

 the growth of the stag's horn. Such an attractive influ- 

 ence on the part of the tissues is quite conceivable as a 

 force assisting in the onward flow of blood, acting along 

 with capillarity." 



It is rather hard to see how an attractive influence on 

 the part of the tissues can assist in the onward flow of 

 blood, even when it is assisted by capillarity. At any 

 rate this statement is sure to be devoured greedily by the 

 studious fool, who will thereafter reproduce it on all 

 possible occasions, probably as the chief factor in the 

 circulation of the blood. 



In discussing the nervous mechanism of respiration. 



