PREFACE. 



Some years of contact with students of comparative (com- 

 monly called veterinary) medicine, and a fair knowledge of 

 the actual needs of the practitioner of this department of the 

 medical art, have convinced me that the time has fuUy come 

 when the text-books of physiology provided for students of 

 human medicine, and which the former classes have hitherto 

 been compelled to use, should be replaced by works written 

 to meet their special wants and possibilities. In fact, so dif- 

 ferent from man are most of the animals which the veterina- 

 rian is called upon to treat, and therefore to understand, in 

 health as well as in disease, that only the absence of suitable . 

 works of a special character can justify the use of those that 

 confessedly treat of man alone. 



Unfortunately, till within the past year the English-speak- 

 ing student of comparative medicine has been without a 

 single work in his own language of the special character re- 

 quired. Within that period two have appeared — the excel- 

 lent but ponderous Physiology of the Domestic Animals, by 

 Prof. Smith, and my own Text-Book of Animal Physiology. 

 It has, therefore, occurred to me that a somewhat smaller 

 work than the latter, embodying the same plan, but with 

 greater specialization for the domestic animals, would com- 

 mend itself to both the students and the practitioners of 

 comparative medicine. In my other work I have endeavored 

 to set before the student a short account of what has been 

 deemed of most importance in general biology ; to furnish a 

 full account of reproduction; to apply these two depart- 

 ments throughout the whole of the rest of the work ; to bring 



