Vlll PREFACE 



chemistry, they are not as a rule capable of applying their knowledge 

 to the elucidation of physiological problems. Hence my present 

 attempt to supply them with the necessary aid. My friend Professor 

 T. G-regor Brodie has made a special study of the subject of hsemo- 

 dynamics, and I owe him my sincerest thanks for the assistance he 

 has given me in revising the part of the present edition which deals 

 with the circulation. 



W. D. HALLIBUBTOK 



KING'S COLLEGE, LONDON, 

 1904. 



AUTHOR'S PREFACE TO THE PRESENT 

 EDITION 



IN the year that has elapsed since the publication of the last 

 edition, I have again subjected the book to a thorough revision. The 

 only parts, however, which have been materially altered are the 

 chapters relating to the special senses, and to the generative organs 

 and development. I am much indebted to Dr C. S. Myers, Lecturer 

 on Experimental Psychology at this College, for his valued help in 

 revising the account given of the special senses; and to Professor 

 Arthur Kobinson, now of Birmingham University, for great assistance 

 in rewriting the sections relating to generation and development. In 

 former editions the chick has been largely taken as the type of a 

 developing vertebrate animal ; now the main descriptions relate to the 

 mammalian embryo. This has involved the disappearance of numer- 

 ous old illustrations, and the introduction of as many as thirty-six 

 new ones. 



W. D. HALLIBUBTON. 



KING'S COLLEGE, LONDON, 

 1905. 



