PREFACE TO THE EIGHTH EDITION 



IN the midst of arms the laboratories #re silent, and if the book has 

 not been quite so extensively revised in this as in the previous 

 edition there is only too valid an excuse in the withering influence 

 of the war upon the output of new work. Nevertheless, consider- 

 able changes and additions have been made, especially in the 

 portions dealing with the chemical phenomena of respiration, the 

 functions of the endocrine organs and metabolism. Some of the 

 newer calorimetric work has been more adequately taken account 

 of. The filtration-reabsorption theory of urine formation, as 

 recently formulated by Professor Cushny, is discussed, although 

 necessarily in less detail than its importance merits. Some of the 

 more recent results of the examination of the mechanics of the 

 circulation by optical methods of recording have been noticed. 

 Several of the old illustrations have been omitted and a considerable 

 number of new ones added. In deference to the opinion of a 

 number of teachers a bibliography has been inserted in the form of 

 an appendix. Most of the references are to papers written in 

 English, as these will necessarily be of the most general use, and in 

 any case will usually contain references to the most important papers 

 in other languages. An exception is made in favour of monographs 

 which are themselves provided with extensive bibliographies. 

 Recent communications are often cited in preference to older ones 

 on the same subject, not because the new work is necessarily 

 better or more important than the old, but because recent papers 

 will, as a matter of course, refer to previous publications. 



Despite suggestions made from time to time* by critical friends 

 and friendly critics (it is curious how little there is of cross division 

 here), the Practical Exercises have been retained in their original 

 place at the end of the related chapters. The author has been 

 asked more than once whether it would not be better to collect 

 them into a separate small volume, for greater convenience of use 

 in the laboratory. Apart from the fact that this would entail a not 

 inconsiderable duplication of material, including illustrations, the 

 exercises in their present form and position being supplemented freely 

 by cross-references to the text, the suggested change would run 

 counter to all the ideas of the author as to the relation between text- 

 book and practical work in the study of a science like physiology. 

 But for the exigencies of curricula, which necessarily, having to reckon 



