92 
N. H. PAARIDN. 
pains begin, and, under normal conditions, the afterbirth is ex¬ 
pelled in the course of the first twenty-four hours; otherwise it is 
often the case that it will not be discharged without assistance. 
V arious circumstances may cause its retention; either disturb¬ 
ances in the function of the uterus, a faulty condition of the 
secnndines themselves, or abnormal connections of these with 
the uterus. 
The uterus, whose muscular fibres during gestation have be¬ 
come considerably extended, already begins to contract actively 
with the advent of the labor pains, and this, together with simul¬ 
taneous contractions of the abdominal muscles, causes the opening 
of the os uteri, the escape of the liquor amnii, and the birth of 
the calf. As the empty uterus is then no longer influenced by 
the abdominal muscles, the expulsion of the afterbirth is effected 
alone by the uterine contractions ; but various irregularities may 
prevent its expulsion. Among these may be mentioned, a poor 
and anaemic condition of the cow ; beginning calving fever; 
advanced age; and protracted and difficult labor—under 
which circumstances the normal contractions of the uterus 
do not occur, or at least are not sufficiently effective. 
When the calf leaves the uterus, a powerful stimulus to its 
action is removed; and this stimulus the afterbirth is quite in¬ 
adequate to supply. If the uterus, from the causes just mentioned 
above, fails in discharging the afterbirth, it becomes accustomed 
as it were, to its presence, and it no longer acts as a stimulus, but 
it remains with the uterus imperfectly contracted around it. 
Gradually, the uterus, in a soft and flabby condition, descends 
beneath the brim of the pelvis, in a position considerably lower 
than the vagina and external genital parts. The moisture from 
the afterbirth, which latter is now a foreign body, and mucous 
secreted from the mucous membrane of the uterus, tend to soften 
the walls of the latter, often rendering them considerably tender. 
Thus the afterbirth is retained until it is removed by artificial 
means, or by its own weight, aided by a recumbent position of the 
cow, slides out through the yet open os, after being detached from 
the cotyledons by decomposition. Of course, the more the uterus 
and the abdominal walls have been expanded during gestation. 
