THE CAUSE OF INFECTIOUS DISEASE. 25! 



energy or the cause, or, in a word, the disposi- 

 tion of men. 



Disease-Stimuli. 



The liberating impulses, as they are called 

 in the inorganic sciences, are called stimuli in 

 speaking of normal life-processes, and we may 

 speak of the particular stimuli that evoke dis- 

 ease as excitants of disease, as Liebig spoke 

 of the excitants of fermentation. 



Through a depression of the physiological 

 organization and a consequent lowering of re- 

 sistance, normal physiological stimuli may 

 become disease stimuli ; or, the organization 

 and resistance remaining the same, a normal 

 stimulus may become more intense and be 

 converted into a disease stimulus ; in other 

 words, the stimulus may come into play only 

 quantitatively. If this be so, it is easy to 

 understand how the kind of effect that we call 

 disease depends qualitatively upon the kind of 

 organ, tissue, or cell concerned, and indeed 

 solely upon these and their internal adjust- 

 ments (Virchow). If the disease stimulus, 

 however, be a living thing, then, according to 

 Koch's conception, this natural law would be 

 summarily abolished and the quality of the 

 disease stimulus, that is to say, the kind of 

 disease-producing bacteria, would determine 



