PREFACE. IX 



with the circulation of the blood, which is so essential for the 

 life of every tissue, one should have some knowledge of nerve 

 and muscle. To begin with nerves and muscles, the mechanisms 

 and the uses of the blood current should be understood ; and so 

 on throughout the various systems, which are so interdependent 

 that, for the thorough comprehension of any one, a knowledge 

 of all is required. 



I have, therefore, adopted the time-honored" plan of commenc- 

 ing with the vegetative systems and following the course of the 

 aliments to their destination and final application, as I believe 

 that this arrangement is open to as few objections as any other 

 known to me. 



I wish here to express my most cordial thanks to many 

 friends who have aided me with kind assistance and advice. 

 I am deeply indebted to Mr. W. Tyrrell Brooks for the great 

 help he afforded me by compiling the chapters on Development; 

 and I feel I cannot sufficiently thank Mr. E. F. Herroun for 

 his untiring and valuable assistance in the revision of the 

 proof-sheets. 



To Mr. G. Hanlon I am indebted for the careful and skillful 

 manner in which he has executed the new wood-cuts, most of 

 which he had to copy from my rough drawings. 



KING'S COLLEGE, LONDON. 



