MANAGEMENT OF THE BROOD MARE 
53 
“Estrum may occur regularly or irregularly in . . . mares which 
are pregnant, most commonly in early pregnancy, but not rarely after 
mid-term, so that the veterinarian must be constantly on his guard in 
examining such animals and must rely upon other signs to arrive at a 
safe conclusion. 
“Estrum is frequently absent in non-pregnant female. The persistence 
of corpus luteum, sometimes of a former pregnancy, may inhibit estrum 
for months. It is only rarely, if ever, that estrum occurs when a large 
corpus lutem exists. 
“Pyrometra also prevents estrum. At times the presence of a very 
small amount of pus in the uterine cavity may prevent estrum for months 
or years. In such cases the yellow body sinks deeply into the center 
of the ovary, the ovarian tissues draw over it, and it remains as a per¬ 
sistent structure, which by failing to atrophy prevents the occurrence of 
estrum. The presence of a macerating or a dessiccating fetus in utero 
ordinarily inhibits estrum for months or years. 
“The Uterine Seal. In the non-pregnant animal there is a normal 
secretion of lubricant mucus in small amounts. When estrum occurs, 
the volume of mucus becomes enormously increased and it flows from the 
vulva. When pregnancy occurs, the mucus of the vagina is decreased in 
amount, ceases to be lubricant, and becomes adhesive. A new type of 
secretion takes place in the cervical canal, having the character of a 
tough gelatin rather than mucus. This fills all the depressions in the 
very irregular cervical canal and becomes massed in a firm body from 
one end of the cervical canal to the other, completely filling it and pro¬ 
jecting forward into the uterine cavity and backward into the vagina. 
The uterine seal, which is highly adhesive, brings about a most thorough 
and efficient sealing of the canal. As a general rule the seal can be 
palpated at the external os uteri of the mare . . . with the finger 
tip within thirty to sixty days after conception. The finger is to be 
pressed carefully and gently against the external os uteri and then 
cautiously withdrawn; if the seal is present it is readily revealed by its 
adhesiveness. 
“Very rarely this seal, or a substnace closely resembling it is found 
in the cervical canal of the non-pregnant animal and may mislead the 
observer. Sometimes when the animal is pregnant, the seal is partly 
or wholly absent. Such is the case in purulent inflammation of the 
cervical canal. In some animals which are to abort as a result of 
cervicitis the seal is not formed, or the formation is very imperfect. 
Consequently the presence of the typical seal not only gives evidence of 
pregnancy, but adds to that a certain feeling of security, suggesting 
that the animal not only is pregnant, but perhaps is safely pregnant 
. . . it is one of the most valuable signs of pregnancy. 
“Palpitation of the Uterus per Rectum . This is one of the most valuable 
means. After conception the uterus undergoes prompt and marked 
changes in volume, form, consistence, and location. 
“. . . In pregnancy the uterus is smooth and even in outline, firm, 
tense and fluctuating ... In the mare owing to the crucial uterus, 
the embryo may develop transversely in both horns, resulting in equal 
volume. At the region of the internal os uteri the superior uterine wall 
rises up suddenly like a terrace, instead of sloping forward gradually as 
is observed in case of pus or lymph distending the organ. The firmness 
of the uterine wall is in marked contrast also to the character of the 
walls when the organ is distended with pus or lymph. In pregnancy the 
uterus is distinctly firm. It exhibits to the touch a sense of vigor and 
life. When lymph distends the uterus, the walls may be thin as in 
pregnancy, but they are soft and placid and the horns are probably 
equally filled. When the organ is distended with pus, the contents do 
not move as freely as the fetal liquids. The uterine walls are soft and 
