2 HUMAN PHYSIOLOGY. 



This may naturally be divided into: 



1. Special physiology, the object of which is a study of the vital phenomena 

 or functions exhibited by the organs of any individual animal. 



2. Comparative physiology, the object of which is a comparison of the vital 

 phenomena or functions exhibited by the organs of two or more animals, 

 with a view to unfolding their points of resemblance or dissimilarity. 



Human physiology is that department of physiologic science which has 

 for its object the study of the functions of the organs of the human body in a 

 state of health. 



Inasmuch as the study of function, or physiology, is associated with and 

 dependent on a knowledge of structure, or anatomy, it is essential that the 

 student should have a general acquaintance not only with the structure of 

 man, but with that of typical forms of lower animal life as well. 



If the body of any animal be dissected, it will be found to be composed of a 

 number of well-defined structures, such as heart, lungs, stomach, brain, eye, etc., 

 to which the term organ was originally applied, for the reason that they were 

 supposed to be instruments capable of performing some important act or func- 

 tion in the general activities of the body. Though the term organ is usually 

 employed to designate the larger and more familiar structures just mentioned, 

 it is equally applicable to a large number of other structures which, though 

 possibly less obvious, are equally important in maintaining the life of the in- 

 dividual e, g., bones, muscles, nerves, skin, teeth, glands, blood-vessels, etc. 

 Indeed, any complexly organized structure capable of performing some func- 

 tion may be described as an organ. A description of the various organs 

 which make up the body of an animal, their external form, their internal 

 arrangement, their relations to one another, constitutes the science of ANIMAL 

 ANATOMY. 



This may naturally be divided into: 



1. Special anatomy, the object of which is the investigation of the construction, 

 form, and arrangement of the organs of any individual animal. 



2. Comparative anatomy, the object of which is a comparison of the organs of 

 two or more animals, with a view to determining their points of resem- 

 blance or dissimilarity. 



If the organs, however, are subjected to a further analysis, they can be 

 resolved into simple structures, apparently homogeneous, to which the name 

 tissue has been given e. g., epithelial, connective, muscle, and nerve tissue. 

 When the tissues are subjected to microscopic analysis, it is found that they 

 are not homogeneous in structure, but composed of still simpler elements, 

 termed cells and fibers. The investigation of the internal structure of the 



