VI PREFACE. 



on animals, are applicable to the vital processes of the 

 domestic animals. 



Modern physiology rests on the application through 

 experimental research of the laws of physics and chemistry. 

 The fundamental principles of these sciences in their relation 

 to biology have been, therefore, discussed somewhat at 

 length. Experience has taught that a comprehension of the 

 laws of life in the higher mammals is best attained after a 

 familiarization with the vital operation of lower forms. The 

 first part of this book, therefore, deals with the general laws 

 of life, while in the second part these principles are applied 

 to the study of the vital operations in the domestic animals, 

 the study of each function being introduced by a sketch of 

 the mode of development of the mechanism by which that 

 function, in passing from lower to higher forms, is accom- 

 plished. 



As far as possible the author has acknowledged in the 

 text his indebtedness to various authorities for the matter 

 or manner of his subject, though references to publications, 

 as tending to confuse the student, have been omitted. 



For illustrations the author is indebted to the liberality 

 of the publisher, Mr. Davis, and to Messrs. Blakiston and 

 H. C. Lea & Co., of Philadelphia ; Appleton, Win. Wood & Co., 

 and Macmillan, of New York; Ferdinand Enke, Stuttgart; 

 Engelmann and F. C. W. Vogel, Leipsic; Paul Parey, Berlin; 

 W. Braumiiller, Vienna; Carl Winter, Heidelberg; Hachette & 

 Cie, Bailliere & Fils, Asselin & Cie, Paris; Simpkin, Marshall 

 & Co., London; Moritz Perles, Vienna, and Hirschwald, Berlin. 



ROBERT MEADE SMITH. 



Philadelphia : 



332 South Twenty-First Street, 

 January 3, 1889. 



