i 
Very generally the bull was first held to be responsible 
and only after changing him several times attention was paid 
to the cows and an explanation sought there. 
In the veterinary literature a number of probable causes 
were discussed and as many treatments proposed. The most 
complete work was done in Switzerland. 
Zschokke (Zurich), who worked extensively on the ques- 
tion, gives a number of reasons for the sterility of cattle. 
He does not, however, specify the importance of the different 
causes. 
I think it advantageous to discuss Zschokke’s work in 
detail as he not only had a large amount of clinical material 
at his disposal, but also bases his conclusions on many 
diligent histological examinations. 
Zschokke claims that sterility is in general an ailment of 
the cow, in a less degree of the bull. In the latter the follow- 
ing conditions are observed: 1. Difficulties in executing the 
mating act, due to obesity, pathological conditions of the 
penis, the legs or the feet: 2. Disinclination to mate, on ac- 
count of malnutrition, lack of exercise, exhaustion by too 
frequent cohabitations and several other pathological condi- 
tions; 3 Impossibility to mate on account of the painful con- 
dition of the preputium or of the penis, paralysis of the penis, 
fracture of the penis or a rupture in the cavernous parts of 
it; 4. Complete impotence through pathological changes in 
the sexual glands. 
Sometimes no lesions can be found in the sexual glands, 
even if a careful postmortem is made, which would explain 
the permanent or periodic impotence; in such cases a les- 
sened motility of the spermatozooa is supposed. This form 
of impotence is specially often found in inbred animals and 
there again most frequently in pigs. In the most cases of 
complete impotence it is possible to demonstrate lesions in 
the sexual glands; there are innate and acquired lesions, the 
latter much more prevalent. The acquired lesions are of 
either traumatic or infectious origin. 
