The Avenue of Infectioyi 487 



their tails, it is easy to understand how this comparatively direct 

 transmission of the disease may occur. 



On the other hand, the infection may occur in a comparatively 

 indirect manner, since mares in the same enclosure habitually rub 

 against objects of various kinds, and thus, one after another, come 

 in contact with the same object. If they use a common sleeping 

 ground, the bedding, earth or herbage becomes soiled by the 

 discharges from an aborted animal and the infection is obtained 

 therefrom by a pregnant mare. Thus it spreads rapidly and 

 freely, whether the animals are confined in close proximity in 

 the stable or whether they are running free in extensive pastures 

 or even upon comparatively open ranges. It is not known 

 whether the disease can spread through the air without an in- 

 termediary bearer. 



Some investigators of the infectious abortion of cows have 

 come to the conclusion that the bull plays a highly important 

 part in the distribution of the disease and in the introduction of 

 the infection from one stable to another. The conclusion has 

 been drawn from this that the male animal in general constitutes 

 an efficient bearer of the disease, although himself not affected 

 by it in any visible manner. It does not seem that the stallion 

 plays a very important part in the distribution of infectious abor- 

 tion of the mare. The incubation of the disease is so rapid that, 

 if the infection is transmitted to the mare by the stallion, it 

 would appear that abortion would occur very early and would 

 not be observed. It is not safe to conclude, however, that he 

 does not spread the disease in some cases. 



The stallion may otherwise be an important factor in the 

 spread of abortion by copulation. We do not know how long 

 the micro-organism of infectious abortion may live in the vulva 

 and vagina of a mare whicli is not pregnant or which has but 

 recently been bred. It is quite possible that a stallion which 

 had first served an aborted mare, and then covered a healthy one, 

 might transfer the organisms to the genital canal of the health}' 

 animal, which would then act as a bearer of the disease to any 

 pregnant mares with which she might soon come in contact. 



Reasoning from the observations of Guillerey, that the soiled 

 hands or shoes of persons, or the soiled blanket or harness from an 

 aborted mare, can carry the disease from one stable to another, it 

 might readily follow that a gelding or other horse placed in 



