iv PREFACE. 



text-book, I have carried out the same idea, striving to teach, systemati- 

 cally and with uniform emphasis, what students of medicine are expected 

 to learn in physiology, and avoiding elaborate discussions of subjects not 

 directly connected with practical medicine, surgery, and obstetrics. While 

 I have referred to my original observations upon the location of the sense 

 of want of air in the general system, the new excretory function of the 

 liver, the function of glycogenesis, the influence of muscular exercise upon 

 the elimination of urea, etc., I have not considered these subjects with 

 great minuteness and have generally referred the reader to monographs for 

 the details of my experiments. 



Finally, in presenting this work to the medical profession, I cannot 

 refrain from an expression of my acknowledgments to the publishers, who 

 have spared nothing in carrying out my views and have devoted special 

 pains to the mechanical execution of the illustrations. 



YORK, November, 1875. 



