REVIEWS 509 



of the most fascinating and important advances of biological science. Hence it is 

 almost inaccessible to the ordinary public, and even medical practitioners, health 

 officers, and sanitary inspectors have rarely the time necessary to delve in these 

 mines and extract the vital parts of the information they contain. The present 

 volume is, so far as we know, the only one of reasonable size that does this for 

 them in a thoroughly satisfactory way. 



The author in his preface defends the time and labour he has spent on the 

 production of this book against those who deem all time not spent in research as 

 time wasted. But good work never requires an apology, and in probably no 

 branch of medical biology was such a book more urgently needed. It contains 

 an extraordinary amount of information for its handy size, and all in a readily 

 assimilable form. The illustrations and copious index add to its value. 



The parasites are arranged under three great Zoological groups — the Protozoa, 

 the Worms, and the Arthropods. The first two groups, of course, include by far 

 the larger number of serious parasites, and the last, although not such dangerous 

 forms in themselves, are of enormous importance because of the role they play in 

 the transmission of disease. Then, too, they are of larger size, and so more easily 

 recognised and controlled. Each group is dealt with in turn, and the various 

 sections treated individually after the particular section has had a general 

 introduction. In every case the diagnosis, distribution, and treatment of the 

 disease is discussed. 



The style adopted is throughout vigorous, and even if somewhat " American " 

 for the British reader, it is nevertheless incisive and clear. The author's remarks 

 on Syphilis and on Vivisection are worth reading and will be pretty generally 

 agreed to. 



It is a volume that can be heartily commended, and its utility and force should 

 assure it a wide circle of readers both professional and lay, for its treatment of the 

 subject is such that it can be readily followed by all. 



C. H. O'D. 



ENGINEERING 



Alternating Current Electrical Engineering. By Philip Kemp, M.Sc, 

 A.M.I.E.E. [Pp. xi +494, with 399 illustrations.] (London: Macmillan 

 & Co., 1918. Price 17s. net.) 



There are many text-books available for students of alternating current tech- 

 nology ; some of the older ones were treatises on applied mathematics in which 

 the conditions controlling the flow of currents in alternating current circuits were 

 almost a by-product of a mass of mathematical analysis, at the other extreme has 

 been the text-book which has attempted to deal with the subject without the use of 

 any higher mathematical analysis at all — a method which, though useful for many 

 evening-class technical students, was unnecessarily laborious, and clumsy in 

 many of its developments. 



This book strikes a mean between the two extremes, and the result is a text- 

 book which should have a wide field of usefulness. 



The book starts with a definition of the alternating current, its frequency, 

 amplitude, and wave shape ; it then proceeds to discuss practical methods of 

 measurement. This is followed by the study of the effect of Resistance and 

 Self-induction in an alternating current circuit. 



Since the book is intended primarily for those not possessing much knowledge 

 of mathematics, it would seem desirable to substitute one of the well-known 



