GENERAL CONSIDERATIONS, 15 



animals as compared with man, or comparative physiology, 

 and the PHYSIOLOGY OF MAN. The latter, which is the sub- 

 ject of the present work, is peculiarly interesting to the 

 physician, as the basis of all accurate knowledge of the 

 science of medicine. 



In the early history of physiological science, the develop- 

 ment of anatomy necessarily gave us much information con- 

 cerning the functions of the body ; and we now have to 

 acknowledge our continual indebtedness to anatomical inves- 

 tigations, particularly those made with the aid of the micro- 

 scope, for important advancements in physiology. In treating 

 of the subject, it is impossible to neglect what is most appro- 

 priately called the physiological cmatomy of parts, a knowl- 

 edge of which alone enables us, oftentimes, to comprehend 

 their functions. For example, we can scarcely conceive how 

 the anatomy of the circulatory system could be clearly under- 

 stood without giving us a knowledge of its physiology. 



Chemistry, also, when the components of the body are 

 studied in such a way as not to destroy their properties as 

 organic compounds, has a most important bearing on the 

 advancement of physiology. As a striking example of this, 

 we may take the discovery of the properties of the gases of 

 the air and their relations to the blood by Lavoisier, which 

 gave us the first definite ideas regarding the essential phe- 

 nomena of respiration. We are now largely indebted to 

 modern physiological chemistry for a knowledge of many of 

 the essential phenomena of life, and look tq a further develop- 

 ment of this science for an elucidation of many important, 

 but still obscure, questions connected with nutrition. 



Certain physiological functions are in exact accordance 

 with established physical laws; which are competent, for 

 example, to explain the refraction in the structures of the 

 eye, or the conduction of vibrations in the ear. Physical 

 laws are involved in most of the phenomena of life, but are 

 generally more or less modified by the peculiar properties of 

 organized bodies. 



