276 A MANUAL OF BACTERIOLOGY 



has undoubtedly been derived from contamination from 

 a human source, e.g. in an outbreak in Lambeth, Priestley 

 traced the infection to the ulcerated thumb of an employe 

 in a particular dairy which had become infected with 

 virulent diphtheria bacilli, but in others this mode of 

 infection has not been demonstrated, and it has been 

 suggested that certain eruptive conditions on the teats 

 and udder of the cow may be caused by the Klebs-Lofner 

 bacillus and the milk become infected therefrom. Klein l 

 made experiments with a view of determining this point. 

 He inoculated healthy cows in the shoulder with a bouillon 

 culture of the diphtheria bacillus. This caused fever and 

 local swelling, and in about a week a papular and vesicular 

 eruption appeared on the udders and teats. The B. 

 diphtheria was isolated from the contents of the vesicles 

 and also from the milk on the fifth day, but not subse- 

 quently. The cows died in two to four weeks, and the 

 B. diphtheria was obtained from the local lesions. Abbott 2 

 obtained somewhat different results, but Klein 3 points 

 out that these experiments were not performed under 

 exactly the same conditions as his own. 



Klein, Eyre, Dean, and Marshall 4 have isolated the 

 diphtheria bacillus from milk. It is to be noted that 

 diphtheria-like, but non-pathogenic, bacilli are often to be 

 found in milk and cheese (see section on " Milk "). 



Toxins. Diphtheria toxin has not been obtained in a 

 state of purity and its exact chemical nature is unknown. 

 LofHer first investigated the chemical products formed by 

 the diphtheria bacillus, and by precipitating bouillon 

 cultures with alcohol obtained a white toxic substance 

 which he classed among the enzymes. 



Roux and Yersin precipitated the toxin from filtered 



1 Hep. Med. Officer Loc. Gov. Board for 1889 and 1890. 



2 Journ. Path, and Bact., vol. ii, 1894, p. 35. 



3 Ibid. p. 428. 



* Jmirn. of Hygiene, vol. vii. 1907, p. 32 (Refs.). 



