VI 



DISEASES OF THE COW in 



milk, and in three of these he considers the cause to have been 

 the milk of cows suffering from mastitis streptococci. In 

 several cases the milk of these diseased cows, after being 

 stopped, was again mixed with the other milk and sold (owing 

 to change in the milkers), and diarrhoea reappeared amongst 

 the consumers on the same day. Hoist also swallowed 200 c.c. 

 of a milk culture of the streptococci isolated from one of the 

 mastitis cases which had stood for a few hours at 37 C., and 

 in consequence was ill with body pain and some diarrhoea 

 and vomiting. 



At the end of Chapter V. a summary has been given of 

 all the outbreaks which the writer has been able to collect, 

 of sore throat, etc., spread by milk. For many of these a 

 bovine origin has been ascribed. The fact that certain out- 

 breaks do appear to be due to a cow with an infective mastitis 

 is in line with the writer's pathological results. While he 

 found that Streptococcus mastitidis was the usual organism of 

 bovine mastitis, it was not the only type of streptococcus 

 associated with this condition. In one case, for example, a 

 streptococcus of extremely high virulence to rodents was found 

 to be the cause of the mastitis, and this organism in many 

 other ways was quite distinctive from the Streptococcus masti- 

 tidis, and may well have been potentially virulent to man. 

 If we accept the view that the ordinary type of bovine 

 mastitis is due to organisms non-virulent to man, but that in 

 certain uncommon cases this condition is caused by strepto- 

 cocci highly pathogenic to man, it offers a complete explanation 

 of both the bacteriological investigations and the epidemio- 

 logical facts. 



From the practical point of view, it is well to remember 

 that the pathogenic and non- pathogenic types of bovine 

 mastitis are not clinically distinguishable. 



Ulcerated Teats. In addition to the diseases of cows already 

 described, in which the teat eruption is part of a general con- 

 stitutional disturbance such as cow-pox, not infrequently teat 

 ulcerations and eruptions are met with in cows which seemingly 

 are in perfect health. The cowman speaks of them as " sore 

 teats," usually applies some local treatment, and neither notifies 

 the Medical Officer of Health nor calls in a veterinary surgeon 

 to treat them. When a veterinary surgeon is called in or meets 



