PREFACE TO THE FIRST EDITION. 



THIS volume is offered to the medical profession of the United 

 States as a text-book for students, and also as a means of Commu- 

 nicating, in a condensed form, such new facts and ideas in physio- 

 logy as have marked the progress of the science within a recent 

 period. Many of these topics are of great practical importance to 

 the medical man, as influencing, in various ways, his views on 

 pathology and therapeutics; and they are all of interest for the 

 physician who desires to keep pace with the annual advance of his 

 profession, as indicating the present position and extent of one of 

 the most progressive of the departments of medicine. 



It has been the object of the author, more particularly, to pre- 

 sent, at the same time with the conclusions which physiologists 

 have been led to adopt on any particular subject, the experimental 

 basis upon which those conclusions are founded; and he has en- 

 deavored, so far as possible, to establish or corroborate them by 

 original investigation, or by a repetition of the labors of others. 

 This is more especially the case in that part of the book (Section 

 I.) devoted to the function of Nutrition ; and as a general thing, 

 throughout the work, any statement of experimental facts, not 

 expressly referred to the authority of some other writer, is given 

 by the author as the result of direct personal observation. 



The illustrations for the work have been prepared with special 

 reference to the subject-matter; and it is hoped that they will be 

 found of such a character as materially to assist the student in 

 comprehending the most important and intricate parts of the sub- 

 ject. It is more particularly in the departments of the Nervous 

 System and Embryonic Development that simple, clear, and faithful 



