3i6 MICRO-ORGANISMS AND DISEASE [chap. 



contagiuin from sewers is maintained by some sanitarians. 

 Lastly, it has been shown by Mr. Power, Dr. Mason, and . 

 Dr. Philpott that in certain epidemics of diphtheria (York-- 

 town and Camberley, Barking, Croydon), while the milk 

 was the vehicle of infection, the milk did not receive its 

 infective power from a human source. 



Several epidemics of imilk diphtheria, in which fouHng of 

 the milk with human diphtheritic material could not be 

 demonstrated, but, on the other hand, could be excluded, 

 have of late years become known, and in these cases the 

 suspicion attached itself to the cows, for it could be shown 

 that there existed on the farms concerned no other condition 

 which in any way could account for the infectivity of the 

 milk ; besides, this infectivity was inherent to the milk over 

 a certain period. In the case of the Yorktown and Cam- 

 berley epidemic (see Mr. Power's Report in the volume of 

 the Medical Officer of the Local Government Board for 

 1 886) the cows were certified by a veterinary surgeon to 

 have been in good health, though even several days after the 

 human diphtheria cases had ceased to occur two of the 

 cows showed some slight signs of " chaps " on their teats. 

 Mr. Power saw at the farm one cow which had suffered from 

 chapped teats in October, 1886 (the month in which the 

 epidemic occurred), and which still had at the beginning of 

 November a scab or crust at the site of a "chap.'' At 

 Barking the cows whose milk produced the diphtheria (in 

 1888) suffered from a distinctly contagious eruptive disease 

 on the teats and udder, showing itself in sores covered with 

 brown black crusts. The same was noticed in connection 

 with an outbreak of diphtheria (through milk) at Croydon, 

 November, 1S90. The question which was therefore con- 

 sidered important to decide was this : Can cows be infected 

 with the bacillus diphtherise ? During the years 1889, 1890, 



