Facts bearing on acquired immunity 237 



gation carried out in collaboration with di Mattei, made an unexpected 

 announcement. He said he believed that he was justified in affirm- 

 ing that the acquired immunity of rabbits against the bacillus of 

 swine erysipelas is due to the formation, in the fluids of the body, of 

 an antiseptic substance which very quickly destroys this organism. 

 This substance, secreted by the cells of the vaccinated animal, was 

 supposed to act after the fashion of a solution of bichloride of mercury 

 and to kill a large number of bacilli, introduced subcutaneously, in from 

 15 to 25 minutes. This discovery was not confirmed. In a series 

 of experiments that I carried out 1 with the object of clearing up 

 this question, and made under conditions as favourable as possible 

 for the demonstration of the supposed bactericidal secretion, this 

 action was never manifested. Not only did the virulent bacilli of 

 swine erysipelas, when injected subcutaneously into well vaccinated 

 rabbits, remain alive in the subcutaneous exudation for hours and 

 even days, but the attenuated bacilli of Pasteur's vaccines likewise 

 remained intact. These bacilli when introduced into the anterior 

 .chamber of the eye survived for even a longer period. Here, as 

 beneath the skin, the injection of the bacilli induced an exudation 

 rich in leucocytes, amongst which microphages predominated. These 

 phagocytes at once began to seize the bacilli which were destroyed 

 not in the fluid of the exudation but within the leucocytes. Long 

 after all the bacilli had been ingested, 24 hours and more after 

 inoculation, the sowing of the exudation frequently gave growths 

 in appropriate media. 



Emmerich 2 sought by new experiments to remove these objections, 

 but he found that the bacilli of swine erysipelas did not disappear [250] 

 from the vaccinated animal until some 8 or 10 hours after they 

 had been introduced. There is, therefore, no longer any question 

 of a rapid bactericidal action at all comparable to that of corrosive 

 sublimate, which would destroy the introduced bacilli in less than an 

 hour. The limit of 8 to 10 hours, accepted by Emmerich, is still too 

 short and is not in accordance with my experiments ; but even this was 

 quite suflicient for the appearance of a free phagocytosis, a condition 

 that really occurs. Emmerich has not directed his researches in this 

 direction, and his theoretical conclusions did not in the least weaken 

 the value of my arguments drawn from the demonstration of the 

 ingestion and intracellular destruction of the bacilli by phagocytes. 



1 Ann. de VInst. Pasteur, Paris, 1889, t. in, p. 28.9. 



2 Arch.f. Hyg., Miinchen u. Leipzig, 1891, Bd. xn, S. 275. 



