534 SCIENCE PROGRESS 



engineering distribution problems. As the preface says, it probably contains too 

 much. It is easy to criticise and to suggest that the general engineer, for whom 

 the book is intended, does not want to know all the methods for measuring low 

 resistances, for comparing standards, for testing the magnetic quality of iron, the 

 theory of the fluxmeter and so forth ; but " extras," if one may call them by that 

 name, very often prove extremely useful (for there is nothing described that cannot 

 be used by the engineer for practical purposes), and it is better, generally, to have 

 too much rather than too little. 



The book lays down with great clearness and with the use of only the simplest 

 mathematics the fundamental principles underlying electrical measurements, the 

 general laws that must be observed in obtaining an economical distribution system 

 for electric power, the laws of electrostatics which are of practical importance in 

 the design of cables and overhead lines working at high pressure, the laws of 

 magnetism, and some of their applications to electro-magnets. There is a very 

 useful chapter on units, and at the end of the book a short introduction to the 

 principles of alternating current working. Any one with experience in the in- 

 struction of engineering students knows how difficult it is to decide what things 

 must be left out in a course of this kind. There are so many subjects for which 

 a case can.be made out, that they may, and probably will, be of value to the 

 general engineer. So far as it goes, Prof. Kapp's book is one of the best selections 

 that there is, though one may express the belief that it would have been of more 

 general utility if the price had been lower. There are other books of the same 

 kind that cover nearly the same ground, though not possibly with the same 

 thoroughness and breadth of treatment, which may be bought for half what 

 this book costs. It is to be hoped that the publishers may find it possible in later 

 editions to bring it more within the reach of the young engineers who are likely 

 to use it. 



PHYSIOLOGY 



The Respiratory Exchange in Animals and Man. By August Krogh, Ph.D. 

 Reader in Zoophysiology, University of Copenhagen. [Pp. viii + 173, with 

 35 figures.] (London : Longmans, Green & Co., 1916. Price 6.y. net.) 



Dr. Krogh'S Respiratory Exchange is one of the best monographs of the 

 excellent series edited by Prof. Hopkins and Dr. Plimmer. 



It deals chiefly with the quantitative aspect of this exchange and takes no count 

 of the physiological mechanisms involved, but (in spite of a prefatory disclaimer) 

 is, within its limits, a really exhaustive review of the subject. 



Methods of measuring the exchange are fully described, though from the 

 theoretical rather than from the practical experimental standpoint. " Standard 

 Metabolism " is defined as that corresponding to a minimum functional activity ; 

 and the bulk of the volume is devoted to this standard metabolism — to its 

 variations under the influence of internal and external factors, to its alterations 

 during the life-cycle, and to the differences exhibited in it by different species, and 

 by more widely divergent groups of animals. 



The book is no mere compilation — Dr. Krogh has, himself, worked over much 

 of the ground, and is, consequently, able to furnish many original data and to deal 

 with the work of others from a really critical standpoint. Its subject-matter is 

 chemical rather than physical, and, though dealing with chemical physiology 

 rather than with physiological chemistry, it will be of particular interest and value 

 to those concerned with the chemical details of animal metabolism. In style it is 



