CAUSES OF DISEASE. 5 



either so large a surface of the cuticle was destroyed 

 that the respiratory and excretory functions of the skin 

 were interrupted, so that poisoning followed the reten- 

 tion of products which should have been excreted from 

 the body; or, poisoning resulted from absorption of the 

 detrimental products into which the skin was converted 

 by the fire. 



Similarly, in diseases the result of mechanical forces, 

 while the earliest phenomena are the direct result of 

 the injury (shock, for example), the later reactions 

 follow as a sequel to the absorption of dead tissues 

 and inflammatory products. Indeed, reconstruction of 

 tissues, e.g., bone, etc., is initiated by these very prod- 

 ucts being absorbed, and, thereby reflexly irritating 

 into action those tissues and functions that bring about 

 repair. 



The fourth group into which we divide 



Animate the agents of disease is the animate. 



Agents. Animate agents comprise two classes, 



parasites and infectious agents, both of 



which may be found among either the animal or 



vegetable kingdom. 



Before the dawn of bacteriology, phys- 

 Infectious icians had already applied the term, infec- 

 Agents. tious, to diseases that, symptomatically, 



conformed to a certain type and were con- 

 veyed through the air. Early in their career, bacteriol- 



