126 MICROBES AND TOXINS 



In the infections due to a well characterised microbe, 

 capable of itself of causing the disease, the associated bacteria 

 most often act by turning upon themselves the phagocytic 

 attack ; their r61e is thus secondary. 



The study has hardly commenced of those bacterial associa- 

 tions which have no specific pathogenic power, but which act 

 nevertheless favourably or the reverse by the products of their 

 metabolism. Their sphere is chiefly the alimentary canal, and, 

 according as the dominant flora of the intestine is acid pro- 

 ducing or produces indols and phenols, the general health 

 escapes or is subject to the action of the sclerosing toxins. 

 These microbial associations thus constitute a certain condition 

 or disposition rather than a true disease. There can be 

 distinguished in it a fundamental flora and an accidental flora, 

 and these can be modified by fortifying one species at the 

 expense of the others ; it is in this that bacteriotherapy 

 consists. 



In the mouth, microbial associations produce a disposition, 

 more or less marked, towards the development of inflammations 

 of the throat. 



The body presents a field capable of infinite variations ; we 

 have to reckon with species, age, and physiological conditions : 

 hunger, cold, and fatigue. Experiment alone could teach us 

 that a mammal, such as the rabbit, is more sensitive to avian 

 tuberculosis than to the tuberculosis of mammals, or that the 

 rabbit is extremely sensitive to the bacillus of fowl-cholera and 

 the pigeon to that of swine-erysipelas. The Algerian sheep is 

 more resistant to sheep-pox than the sheep of Camargue. In 

 general very young animals are more sensitive than adults, 

 yet the young pig hardly ever contracts swine-erysipelas under 

 three months. 



Hunger, heat, or cold, and fatigue act by depressing the 

 phagocytic defences. 



Paths of Penetration into the Body. — The mosquito 

 inoculates the virus which it carries either under the skin 

 or directly into a blood-vessel. The spirochsete produces 

 syphilis only when it is inoculated strictly in the subcutaneous 



