98 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



udder they are round; on the teats oblong, with the great- 

 est diameter parallel with the length of the teat. In a 

 day or two they change into vesicles of a bluish-white 

 or yellowish- white color. The vesicles ripen into pustules 

 in eight or ten days and a depression or umbilication 

 appears in the top, after which they rupture and leave 

 an ulcer, or dry and heal under a scab. They may be 

 ruptured during milking before they are ripe. 



The milk may become thin, bluish, and of lighter 

 specific gravity than normal; it may be nauseating and 

 may coagulate very readily. The acidity may be below 

 normal. These changes, however, do not always occur. 

 When the disease is complicated with parenchymatous 

 mastitis, as sometimes happens, then the milk undergoes 

 the pronounced changes which occur in the latter con- 

 dition (see page 109). 



Cowpox is transmitted from cow to cow by the milker 

 and by infected bedding, fodder, and stalls. The disease 

 is also transmissible from the cow to man through milk. 

 There is no proof that the virus is excreted through the 

 udder, but as the pox are located on the teats and the 

 adjacent parts of the udder it is practically impossible 

 to draw the milk without the virus contained in the ves- 

 icles and pustules getting into it. Stern saw cowpox 

 transmitted to a large number of children by milk from 

 a dairy in which the disease was enzootic. The children 

 were affected with an eruption on the face which healed 

 under a scab. Not many such observations have been 

 recorded, however. The reason for this is that the general 

 custom of vaccinating against smallpox has rendered 

 most persons immune to the disease. The transmission 

 of the disease to the milkers by direct infection of wounds 

 on the hands or fingers has been more frequently ob- 



