154 ESSAYS ON BACTERIOLOGY. 



teria have been shown to develop more certainly in 

 animals after great fatigue. Pus microbes, anthrax 

 bacilli, and other microbes, have been found to infect 

 with more certainty and violence certain animals in 

 which an artificial anemia has been produced by 

 bleeding. One of Pasteur's classical experiments con- 

 sisted in rendering hens, ordinarily unsusceptible, sus- 

 ceptible to anthrax by artificial cooling of their 

 bodies; and conversely, artificial elevation of the tem- 

 perature of frogs has changed their natural immunity 

 into susceptibility to anthrax. A similar result has 

 been shown to follow in animals deprived of water. 

 Thus many of the things included under the general 

 term bad hygiene have been definitely shown to ren- 

 der animals more susceptible to the growth of bacteria. 



Previous disease, as shown by clinical experience 

 and by definite bacteriological experiment, may pre- 

 dispose to subsequent infection, though this agency is 

 most often seen to act as a local rather than a general 

 predisposing factor. 



Local, like general predisposition, may be brought 

 about by an indefinite number and variety of things 

 which temporarily or permanently injure the tissues. 

 Here belong traumatisms, local inflammations, ante- 

 cedent local or general diseases which produce distinct 

 local injury, and serious alterations in the local circu- 

 lation of the blood. 



The result of all such agencies is a locus minoris 

 resistentise, a point of lessened resistance to the en- 



