PEEFAOE TO THE FIKST EDITION. 



IN preparing this text-book for the use of students and practitioners of 

 medicine, I have endeavored to adapt it to the wants of the profession, as they 

 have appeared to me after a considerable experience as a public teacher of hu- 

 man physiology. My large treatise in five volumes is here condensed, and I 

 have omitted bibliographical citations and matters of purely historical interest. 

 Many subjects, which were considered rather elaborately in my larger work, 

 are here presented in a much more concise form. I have added, also, numer- 

 ous illustrations, which I hope may lighten the labors of the student. A few 

 of these are original, but by far the greater part has been selected from relia- 

 ble authorities. I have thought it not without historical interest to reproduce 

 exactly some of the classical engravings from the works of great discoverers, 

 such as illustrations contained in the original editions of Fabricius, Harvey, 

 and Asellius. In addition, I have copied a few of the beautiful microscopi- 

 cal photographs taken at the United States Army Medical Museum by Dr. J. J. 

 Woodward, who kindly furnished them to me and to whom I here express 

 my grateful acknowledgments. I have also to thank M. Sappey for his kind- 

 ness in furnishing electrotypes of many of the superb engravings with which 

 his great work upon anatomy is illustrated. 



My work in five volumes was intended as a book of reference, which I hope 

 will continue to be useful to those who desire an account of the literature of 

 physiology as well as a statement of the facts of the science. I have always 

 endeavored, in public teaching, to avoid giving undue prominence to points in 

 which I might myself be particularly interested from having made them sub- 

 jects of special study or of original research. In my text-book, I have carried 

 out the same idea, striving to teach, systematically 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 medi- 

 cine, surgery, and obstetrics. While I have referred to my original observa- 

 tions 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 influ- 

 ence of muscular exercise upon the elimination of urea, etc., I have not con- 

 sidered 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 me- 

 chanical execution of the illustrations. 



YORK, November, 1875. 



