76 
ure. It can, therefore, be easily understood that an insufficient 
mating act may be passed for a normal one under the cir- 
cumstances. Very often the bulls are exhausted; and not 
infrequently the bull which is the easiest to handle is used 
over and over again, even if the others are quite fresh. The 
most frequent difficulty in this regard is that the bull is in- 
capable or unwilling to breed with the necessary energy. 
The reason may be: too bulky abdominal organs, too long 
hoofs, pains in the tendons or in the joints, or, especially, in- 
flammatory processes of the preputium. The latter are often 
overlooked on account of their chronic character; they may 
be without significance and not deteriorate the qualities of 
the bull, but very often they hinder the animal from perfect- 
ing the mating act with the energy necessary for a fecunda- 
tion. Sometimes these bulls infect the cows, and one is able 
then to notice a few days after the breeding an injection of 
the vaginal mucosa, and exudation. This infection is often 
considered the cause of the sterility, which is usually present, 
but the real cause is the deposition of the sperma in the 
vagina, where it perishes. 
These facts I have found out only of late years; I 
had observed that in some herds which were under quite 
similar ‘conditions of housing and care and where the per- 
centage of metritis infection was rather even too, there 
nevertheless was often an unexplainable difference in the 
percentage of pregnant cows. For instance, in Paere- 
gaard, an estate I mentioned before, the metritis cases 
were more numerous and more malignant than in 
Ladegaard, during the first year of treatment as well 
as in the beginning of the second year, nevertheless 65% of 
the animals compared with 72% in Ladegaard became preg- 
nant. In the second year, however, the percentage of Paere- 
gaard decreased in an inexplicable way, as the metritis cases 
were now no worse than in the other two herds which be- 
longed to the estate. The cause could be only the bulls; 
there were three bulls used for the healthy cows, and one 
