42 Chapter III 



[45] Let us take as an example the bacillus of blue pus. This organism is 

 most widely diffused in human surroundings. According to Schimmel- 

 busch^ it is met with on the skin of the arm-pits and of the inguinal 

 region of one-half of mankind. From the skin it very often passes 

 into the dressings of wounds which then assume the characteristic 

 and so long recognised blue colour. The same bacillus is also found 

 in the intestines of both sick and healthy persons. Jakowski'^ has 

 met with it in the faeces coming from intestinal fistulae in two women 

 who had undergone operations. Now, in spite of these specially 

 favourable conditions for the production of infection, the Bacillus 

 pjjocyaneiis has remained harmless. It is only in children, and even 

 then rarely, that it can be convicted of exciting disease. Man, then, 

 usually enjoys a true natural immunity against the Bacillus pyo- 

 Cyanefiis. And yet it is not to his insusceptibility to the pyocyanic 

 toxin that he is indebted for this immunity. Schaffer^, having in- 

 jected himself in the shoulder with half a c.c. of a sterilised culture 

 of B. pyocyaneus, developed fever and an erysipelatous swelling. 

 Bouchard and Charrin* injected pyocyanic toxin into patients who 

 reacted with more or less fever and by other toxic symptoms. 



Another extremely common saprophyte, the Micrococcus pro- 

 digiosuSf is incapable of setting up an infective disease, but this 

 does not prevent its products from exercising a toxic action, often 

 very grave, in man. The frog, which is refractory to the cholera 

 vibrio, undergoes a fatal intoxication when cholera toxin is injected. 

 One of the most striking examples is furnished in the case of the 

 human tubercle bacillus and tuberculin. Man is much more resistant 

 than is the guinea-pig to the pathogenic action of this organism, 

 yet he is incomparably more susceptible to its toxin (tuberculin). 

 According to the researches of Behring and Kitashima^, the sheep, of 

 all species of mammals, is most susceptible to the tubercular poison ; 

 the Bovidae and the guinea-pig occupy an inferior rank in the scale 

 of susceptibility. On the other hand, the guinea-pig is very sus- 

 ceptible to the tubercle bacillus; the Bovidae are less so and the 



[AQ] sheep is still more resistant to tuberculosis. It is unnecessary to 

 multiply instances. Immunity against microbial infection and against 



1 "Ueber griinen Eiter," Volkmann's Samml. Min. Vortr., No. 62, Leipzig, 1893. 



2 "Processus chimiques dans les intestins de riiomme," Arch. d. sc. biol. de 

 St-Pelersh., 1892, t. i, p. 539; Ztschr. f. Hyg., Leipzig, 1893, Bd. xv, S. 474. 



3 Cited by Schimmelbusch, I.e. 



* Compt. rend. Acad. d. Sc, Paris, 1892, t. ii, p. 1226. 

 ^ Berl. Jdin. Wchnschr., 1901, S. 163. 



