PEEFACE TO THE FIRST EDITION. 



PHYSIOLOGY is the basis of medicine, and the further advance of these 

 sciences depends mainly upon the "experimental method." The 

 medical student, the future physician, should undergo a training in 

 practical physiology, for thereby he learns the most important of all 

 lessons ; he learns to observe, to draw conclusions from his observations, 

 and to unravel the causes of his failures. 



The importance of practical physiology is undoubted, but as to 

 the nature and scope of the experimental work, which is most suitable 

 for the medical student, there is considerable difference of opinion 

 among teachers of physiology. In this country, perhaps, too much 

 stress has been laid upon the physiology of muscle and nerve ; for the 

 hope that a study of the properties of these tissues will unfold the 

 enigma of life is likely ever to remain without consummation. 



An advance in the knowledge of the living organism as a whole, one 

 organ reacting upon another, has been gained by experiments upon the 

 living animal, treated as a unit and not as a collection of separate 

 organs and tissues. Such practical physiology needs extension in the 

 courses of instruction given to students. It should, as far as possible, 

 have a direct relation to medicine. 



The methods which are used in the investigation of the respiratory 

 system, the circulation, the body heat, the nervous system and special 

 senses ; the chemistry of the blood, of digestion, and of urine these are 

 the subjects which are especially required by the clinician. These sub- 

 jects, moreover, afford as excellent a mental training as the study of 

 muscle and nerve. 



In the present work the authors have attempted to give some exten- 

 sion to practical physiology along the lines just indicated. 



The book has been divided into an elementary and an advanced por- 

 tion. Part I. treats of elementary experimental physiology (the 

 physiology of muscle and nerve, circulation, respiration, animal heat, 



