THE MICROBES OF HUMAN DISEASES. 173 



as long as the epidermis of the mucous membrane 

 covering the intestinal canal is healthy. Pasteur has 

 shown that they are not found in the blood of a 

 healthy man, but that the slightest lesion of the 

 mucous membrane suffices to introduce them into the 

 circulation.* This fact was proved by experiments 

 made at Pouilly-le-Fort on sheep, inoculated with the 

 anthrax microbe by means of their foocf. The mortality 

 among these animals was notably increased when 



Fl^s. 77, 78.' Spirochrpte buccalis, and S. plicatilis, b (mixed witb Vibrio rugula, 

 a), microbes in mouth of a healthy mail. 



thistles, bearded grain, or sharp-edged leaves were 

 mixed with their food, so as to cause little wounds in 

 their mouths, each of which served as an entrance for 

 microbes. As long as the microbes are few in number, 

 they perish quickly in the blood ; but when the 

 number is considerable, the organism has not the power 

 to destroy them ; they soon compete with the corpuscles 

 of the blood, and the most serious diseases ensue. 



Miquel estimates the number of spores introduced 

 into the human system by respiration, when the health 



* This is not the case with fishes. Kichet and Ollivier have shown 

 that microbes are normally found in the blood of sea-fish, without 

 affecting their health. 



