CHAPTER XXIII. 



PATHOGENIC BACTERIA OUTSIDE THE BODY. 



Pathogenic bacteria may exist outside the body of the 

 host under a variety of conditions as follows: 

 I. In or on inanimate objects or material. 



(a) As true saprophytes. 



(b) As facultative saprophytes. 



(c) Though obligate parasites, they exist in a latent 



state. 

 II. In or on other animals, or products from them : 



(a) Sick themselves. 



(b) Recovered from illness but carrying the organisms. 



(c) Never sick with the disease but carrying the 



organisms. 



(d) Serving as necessary intermediate hosts for cer- 



tain stages of the parasite — this applies to 



protozoal diseases only, as yet. 

 I. (a) The bacilli of tetanus and malignant edema are 

 widely distributed. There is no evidence that their entrance 

 into the body is at all necessary for the continuation of their 

 life processes, or that one case of either of these diseases 

 ever has any connection with any other case; they are true 

 saprophytes. Manifestly it would be futile to attempt to 

 prevent or eradicate such diseases by attacking the organ- 

 ism in its natural habitat. Bacillus botulinus, which causes 

 a type of meat poisoning in man, does not even multiply 

 in the body, but the disease symptoms are due to a soluble 

 toxin which is produced during its growth outside the body. 

 (b) Organisms like the bacterium of anthrax and the 

 bacillus of black-leg from their local occurrence seem to be 

 distributed from animals infected, though capable of living 

 a saprophytic existence outside the body for years. These 

 can no more be attacked during their saprophytic existence 



