PROTECTIVE INOCULATIONS. 309 



" 1. After the ingestion of sterilized (by heat) and subsequently carbolized 

 agar cultures of cholera bacteria the serum of man acquires an immunizing 

 property as regards the cholera vibrio. 



4k 2. As a result of the ingestion of sterilized agar cultures the individual 

 is protected from infection with virulent cultures of the cholera vibrio by way 

 of the intestine. 



" 3. The discharges of individuals immune against cholera, and to all out- 

 ward appearance in perfect health, may contain a great number of cholera 

 vibrios (in case they are in any way introduced into the intestine) and may 

 thus serve to propagate the malady." 



DIPHTHERIA. 



According to Roux and Yersin, " attenuated varieties " of the diph- 

 theria bacillus may be obtained by cultivating it at a temperature of 

 39.5 to 40 C. in a current of air; and these authors suggest that a 

 similar attenuation of pathogenic power may occur in the fauces of 

 convalescents from the disease, and that possibly the similar non- 

 pathogenic bacilli which have been described by various investigators 

 have originated in this way from the true diphtheria bacillus. These 

 authors further state, in favor of this view, that -from diphtheritic 

 false membrane, preserved by them in a desiccated condition for five 

 months, they obtained numerous colonies of the bacillus in question, 

 but that the cultures were destitute of pathogenic virulence. They 

 say : 



" It is then possible, by commencing with a virulent bacillus of diphtheria, 

 to obtain artificially a bacillus without virulence, quite similar to the attenu- 

 ated bacilli which may be obtained from a benign diphtheritic angina, or even 

 from the mouth of certain persons in good health. This microbe, obtained 

 artificially, resembles completely the pseudo-diphtheritic bacillus ; like it, it 

 grows more abundantly at a low temperature ; it renders bouillon more rap- 

 idly alkaline ; it grows with difficulty in the absence of oxygen." 



Subcutaneous inoculations in guinea-pigs of a small quantity of a 

 pure culture of the bacillus (0.1 to 0.5 cubic centimetre of a bouillon 

 culture) cause death in from one to four or five days. The usual 

 changes observed at the autopsy are 



" An extensive local oedema^ with more or less hyperamiia and ecchymo- 

 wis at the site of inoculation, frequently swollen and reddened lymphatic 

 glands, increased serous fluid in the peritoneum, pleura, and pericardium, 

 enlarged and hemorrhagic suprarenal capsules, occasionally slightly swollen 

 spleen, sometimes fattA degenerations in the liver, kidney, and myocardium. 

 We have always found the Loftier bacilli at the seat of inoculation most 

 abundant in a grayish- white, fibrino-purulent exudate present at the point of 

 inoculation, and becoming fewer at a distance from this, so that the more re- 

 mote parts of the oedematous fluid do not contain any bacilli " (Welch and 

 Abbott). 



The authors quoted agree with Loffler and others in stating that 

 the bacillus is found only at the point of inoculation. In all cases 



