PREFACE. y 



SO short a space of time, encourages me to hope for one 

 equally favorable for this book, which is offered to a pro- 

 fession from which I look for great things in the interests 

 both of man and the lower animals within the next few 

 years. The time has certainly come when medicine must 

 leave the narrow ruts within which it has been confined, and 

 become essentially comparative. To hasten that consumma- 

 tion, so devoutly to be wished, has been the object with which 

 both my earlier and the present work have been written. Un- 

 less the student is infused with the broad comparative spirit 

 in the earliest years of his studies, and guided accordingly, 

 there is no sure guarantee of final success in the widest sense. 

 My publishers again deserve my thanks for the efforts 

 they have made to present this work in their best form. 



Wesley Mills. 



Physiological Labokaio&t, McGill University, 

 MoNTKEAL, Canada, August, 1890. 



