INFLUENCE OF DISEASE UPON MILK 111 



Considering the frequency of the catarrhal and paren- 

 chymatous forms of mastitis in dairy cows, cases of 

 illness in man resulting from the ingestion of milk from 

 cows affected with this disease have not been reported as 

 often as would be expected. There are several reasons 

 for this. The milk from a diseased cow may be diluted 

 with milk from cows in normal condition to such an extent 

 as to render the mixed milk harmless. Furthermore, 

 some of the mastitis bacteria have a relatively low 

 virulence for man. Finally, it rarely happens that the 

 physician is able to establish the connection between the 

 disease in his patient and the cow affected with mastitis, 

 even when milk from the latter is the cause of the disease. 

 Nevertheless, there are on record numerous cases of ill- 

 ness in man caused by the ingestion of milk from cows 

 affected with mastitis, the symptoms in these cases being 

 nausea, vomiting, and diarrhoea, sometimes associated 

 with fever, f aintness, languor, and cramps in the legs. In 

 two instances the milk which was the cause of the disease 

 had been boiled. It is not known whether the illness in 

 these cases was due to a heat-resisting toxin or to bacteria 

 which survived the heat because of the protection fur- 

 nished by the membrane which forms on the surface of 

 milk when it is heated. 



Numerous epidemics of septic sore throat have been 

 reported in which the infection was transmitted by milk. 

 In some of these epidemics, cows affected with strepto- 

 coccic mastitis were found to be the source of the infec- 

 tion, but in the other outbreaks the circumstances seemed 

 to point to the infection of the milk by dairy workers suf- 

 fering from the disease. To account for the persistence of 

 streptococci for several days in the milk supplies involved 

 in the second group of epidemics, the theory has been 



