272 



NATURE 



[August 2s, 1923 



and peripheral nerves. It seems that at their peri- 

 phery these sensory fibres form a branching network, 

 which in some of its functions resembles the diffuse 

 superficial nerve network so widely distributed in the 

 invertebrata. Stimulation of the surface, especially 

 if painful, causes a dilatation of capillaries and small 

 arteries which spreads for some distance round the 

 stimulated spot. There is no evidence that nerve 

 cells are involved in this local reflex, which is therefore 

 regarded as an * axon reflex.' The redness produced 

 by the application of mustard to the skin is an example 

 of this kind of reaction. If pronounced it may go 

 on to the production of increased transudation of 

 fluid from the affected capillaries and to the appearance 

 of a blister. 



After dealing with the local response of the capillary 

 wall to mechanical and chemical stimulation, Krogh 

 proceeds by a series of carefully thought out experi- 

 ments to the demonstration that, throughout life, 

 the calibre of the capillaries is regulated by some 

 diffusible substance present in the blood, and he 

 tracks this substance finally down to the internal 

 secretion of the posterior lobe of the pituitary body. 

 Perfusion of a frog's limb with Ringer's fluid causes 

 wide dilatation of the capillaries and production of 

 dropsy. If, however, the minutest trace of the 

 pituitary hormone is added to the perfusion fluid, 

 the capillaries retain their normal size and no oedema 

 results. 



Having arrived in this way at a knowledge of the 

 factors affecting the calibre of the capillaries and 

 the volume of the flow through the capillaries in any 

 part, Krogh then proceeds to consider the bearing of 

 these results on the main functions of the capillaries, 

 namely, the nutrition of the tissues, the giving off 

 of oxygen from blood to tissue cells, the taking up of 

 carbon dioxide, the exchange of dissolved substances, 

 and the production and absorption of lymph. In a 

 final chapter he deals with various miscellaneous 

 questions closely associated so far as regards their 

 mechanism, such as the production and absorption 

 of intra-ocular fluid, the condition known as surgical 

 shock, and the causation of weals and urticaria under 

 the influence of poisons or in persons of the so-called 

 ' vaso-neurotic ' disposition. 



It is impossible within the limits of a review to do 

 justice to the wealth of new facts and points of view 

 brought out in the course of these lectures. We feel 

 from the outset that we are starting on a voyage of 

 exploration with the author. In every new step our 

 curiosity is aroused before we are presented with the 

 solution. At the same time we are conscious of the 

 intellectual dangers which beset the explorer in these 

 fields. The author states : " The problems of physio- 



NO. 2808, VOL. 112] 



logy are so complicated that, to put it tersely, one 

 cannot expect to be able to reason correctly from the 

 facts for more than five minutes at a stretch " — a 

 healthy state of mind and ver\' similar to that ex- 

 pressed by Harvey when he says that he " began to 

 think with Frascatorius that the movement of the 

 heart was known to God alone." But such difl^culties 

 and dangers only add to the joy of the chase, and we 

 read the book with somewhat the same fascination 

 and interest that our forefathers must have felt when 

 presented with the inmiortal treatise of Harvey. 



The book is written clearly and simply. We can 

 conceive no better book to put into the hands of a 

 student to arouse his interest in the advancing fringe 

 of physiological knowledge and to acquaint him to 

 some extent with the joy and spirit of research. 



E. H. Starli.ng. 



Thermodynamics and Chemistry, 

 (i) Thermodynamics and the Free Energy of Chemical 

 Substances. By Prof. Gilbert Newton Lewis and 

 Prof. Merle Randall. Pp. xxiii -1-653. (London: 

 McGraw-Hill Publishing Co., Ltd., 1923.) 255. 

 (2) Theoretical Chemistry from the Standpoint oj Avo- 

 gadro's Rule and Thermodynamics. By Prof. W. 

 Nernst. Fifth edition. Revised in accordance with 

 the eighth-tenth German edition, by L. W. Codd. 

 Pp. XX 4-922. (London: Macmillan and Co.. Ltd., 

 1923.) 285. net. 

 (i) P70R many years back the published researches 

 JL of G. N. Lewis and his collaborators have 

 occupied a prominent place in the branch of science 

 dealing with the application of thermodynamics to 

 the solution of chemical problems. The book now 

 under review, of which he and his co-worker. Merle 

 Randall, are joint authors, collects and summarises 

 these • researches and places them in position in the 

 general framework of thermodynamics. For this alone 

 all interested in matters pertaining to physico-chemical 

 theory would owe them thanks, but the debt is in- 

 creased by the fact that no better account of modem 

 chemical thermodynamics than appears in this book 

 can be placed in the hands of advanced students. 



The treatment, while remaining in some ways con- 

 ventional, has an individual freshness which makes the 

 volume much more readable and interesting than most 

 treatises on the subject. The material is divided into 

 three parts, the first treating of the foundations of 

 thermodynamics, the second dealing with the special 

 methods of applying the fundamental principles to 

 chemical problems, and the third being devoted to a 

 systematic consideration of the data of thermodynamic 

 chemistry. As might be expected, the notions of 



