16 INTRODUCTION. 



Many of the phenomena of life are made clear by a 

 comparison of the physiology of man with that of the infe- 

 rior animals, which is often simpler and more easily investi- 

 gated. 



As physiology is the natural and only correct basis of 

 pathology, we frequently derive important information as 

 to the functions of parts by studying the effects of disease, 

 by which their functions are modified or abolished. The 

 experiments thus performed by Nature on the human system 

 are frequently more instructive than those which we make 

 on the inferior animals. 



As the complement to anatomy, human and comparative, 

 organic chemistry, and pathology, we have as the most pre- 

 cious and fruitful means of physiological investigation, direct 

 observation of the phenomena of life in man and the inferior 

 animals, and experiments on animals by vivisections. The 

 present condition of physiology is a testimony of the incal- 

 culable value of this method of study. Were it consistent 

 with our plan to follow out the general development of the 

 science from an historical point of view, we should find the 

 names of Harvey, Aselli, Haller, Hales, Spallanzani, Ed- 

 wards, Bichat, Bell, Majendie, and a host of others, bearing 

 witness by their works to the value of vivisections in physio- 

 logical investigations ; to say nothing of the great observers 

 of the present day, who are constantly adding to our knowl- 

 edge. The field would be sterile indeed were it not for 

 experiments on living animals ; and the loss to the science 

 which has for its object -the alleviation of the sufferings of 

 mankind, would have been incalculable, had physiologists 

 been unwilling, from false motives of humanity, to inflict 

 pain upon the lower animals, which is to a certain extent 

 unavoidable in experimentation. 



Physiological literature, in the great Elementa Physiolo- 

 gies, of Haller, which belonged to a past generation, and 

 the elaborate systematic works of Berard, 1 Longet, Muller, 



1 Berard did not live to complete his great work on physiology. He died 



