BACTERIA IN DIPHTHERIA. 365 



The recent researches of Behring show that the blood of immune 

 animals contains some substance which neutralizes the toxic product 

 contained in virulent cultures of the diphtheria bacillus. This effect 

 is said to be produced when blood from such an animal is added to a 

 filtered culture without the body, as well as when the culture is in- 

 jected into the living animal. This remarkable fact, if fully con- 

 firmed by further investigations, opens up a new field of experimen- 

 tal research, and may lead to important results in the therapeutics of 

 this and other infectious diseases. 



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

 diphtheria bacillus maybe 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 investiga- 

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

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

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

 five months, they obtained numerous colonies of the bacillus in ques- 

 tion, 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 attenuated 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 com- 

 pletely the pseudo-diphtheritic bacillus ; like it, it grows more abun- 

 dantly at a low temperature; it renders bouillon more rapidly alkaline; 

 it grows with difficulty in the absence of oxygen. " 



48. PSEUDO-DIPHTHERITIC BACILLUS. 



Loffler, Von Hoffmann, and others have reported finding bacilli 

 which closely resemble the Bacillus diphtherias, but which differ 

 from it chiefly in being non-pathogenic. The following account we 

 take from the latest paper upon the subject by Roux and Yersin 

 (troisieme memoire, 1890). 



Found by Roux and Yersin in mucus from the pharynx and ton- 

 sils of children from forty-five children in Paris hospitals, suffering 

 from various affections, not diphtheritic, fifteen times ; from fifty- 

 nine healthy children in a village school on the seaboard, twenty -six 

 times. Of six children with a simple angina but two furnished cul- 

 tures of this bacillus, while it was obtained in five out of seven cases 

 of measles. 



