CHAPTER III. 



The Causation of the Vital Changes of Protoplasm — Definition of Structure 

 as applied to Living Matter — Proper Method of Studying the Causation 

 of Disease. 



In the latter portion of the last chapter we dealt with the 

 causation of atomic and molecular phenomena in general. Let 

 us now treat of the causation of those atomic and molecular 

 changes occurring within living protoplasm. 



A protoplasmic cell consists of myriads of molecules, and in 

 contemplating the structure of such a cell we must include 

 both the mutual relations of the atomic constituents of the 

 molecules, and the relations which these latter bear amoug them- 

 selves. Protoplasm is often spoken of as homogeneous. If 

 the molecules were regularly arranged throughout the entire 

 cell protoplasm, the latter would be in a sense homogeneous, 

 though still possessing a structure, but we have no right to 

 assume auy such regular arrangement of molecules in proto- 

 plasm ; indeed, we are a priori compelled to conclude otherwise. 

 The fact that the cells of different tissues have different func- 

 tions proves that their structure is different. This follows from 

 the law of causation, but it is not possible for the most 

 accomplished histologist to refer to its proper order every 

 individual cell that is at haphazard given him for examination, 

 though he may recognize them when grouped together into 

 tissues. 



When it is said that protoplasm is homogeneous, it is 

 meant that it is a homogeneous jelly-like matter, which, 

 however, may be moulded into various forms — that is to say, 

 though the general configuration of the cell may differ, it is 

 assumed that the substance of which it is built up is homo- 

 geneous. For instance, nerve ganglion cells, blood corpuscles, 

 and kidney epithelial cells — notably some of them — -are quite 



