DISORDERS OP THE UDDER 273 



recently vaccinated persons. Thereafter, the disease is spread in 

 the herd chiefly by the hands of milkers, but may be transferred 

 from cow to cow by other means. 



The period of incubation is from four to seven days. Then 

 there is a little fever and mild general symptoms of slight ill- 

 ness. There soon appear a few nodules on the udder and teats, 

 the size of a pea or smaller. In a day or two these change to 

 vesicles (blisters) which contain a thin, clear fluid. At eight or 

 ten days the centers of the vesicles become depressed and the 

 contents become purulent (pus). 



A dry scab gradually forms and falls, leaving the typical 

 pitted scar. 



The sores heal nicely unless injured in milking. Small, slow 

 healing ulcers may be caused in this way. 



Treatment. — Little treatment is necessary beyond very careful 

 milking, unless the vesicles are ruptured and the raw surfaces 

 injured, e.g., in milking. Careful handling and a little vaseline 

 or lanoline are then needed. 



