DISEASES OF SHEEP, 47 



part of the same, is at once taken sick ; if, however, such a 

 case is observed, the owner of such an entirely diseased 

 herd may be assured that either he or his employes have 

 neglected the care of his flock. Sheep pox always spreads 

 gradually, and lingers according to the state of the tempera- 

 ture of the air. Infection is accelerated by heat, and con- 

 sequently when sheep are closely kept together in stables 

 during winter-time the disease is very likely to appear. 

 Sheep kept upon cool pastures during wet and windy 

 weather are not so vehemently affected by pox. The 

 average term during which all animals of a large herd 

 become gradually afflicted with pox lasts from three to four 

 months, and in some instances six months. The general 

 rule is, that the shorter the interval of infection the greater 

 the vehemence and danger of the disease, and vice versA. 

 In most cases there are three periods in regard to the pro- 

 gress of infection : The first period begins with the infection 

 of a few animals, which then (in the second period) infect 

 about the third or fourth part of the herd. After a short 

 interval or rest of about sixteen or eighteen days, these in- 

 fected sheep impart the disease to the remaining healthy 

 part of the flock (third period). This may be a conse- 

 quence of the arrival of maturity in each separate case, 

 which maturity happens in nearly the same equal period. 

 Certain animals are more or less disposed to infection, and 

 this may be assigned as a reason why such animals do not 

 become infected at all, or sooner or later. It may be said 

 in this connection that in the average about four to six per 

 cent, of the sheep belonging to a diseased flock are entirely 

 exempt from infection on account of their constitutional 

 disposition. It is extremely rare that all sheep composing 

 a herd are likewise exempt. 



The treatment of an infected herd depends upon differ- 

 ent circumstances, although the greatest care has to be 



