GRANULAR VENEREAL DISEASE AND ABORTION IN CATTLE. 23 
means of the powerful contraction of the thick muscular walls of the 
cervix. 
Invasion of the uterine cavity through the cervical canal from the 
vagina is further guarded by a series of transverse muco-muscular 
projections directed sharply toward the vagina. These barriers are 
one-half to one inch in length and act as encircling valves directed 
toward the vagina in a manner to prevent ingress from the vagina by 
deflecting any invader from the cervical canal into the cul-de-sac of 
the valves, while permitting a more free egress from the uterine 
cavity. 
The anatomical arrangement of the walls of the cervical canal 
results in the channel being firmly closed in the normal nonpregnant 
cow which has not recently calved and is not in estrum. The closure 
is so firm, the canal so tortuous, and the valvular barriers are so 
effective that it is impracticable to insert a man's finger or even a 
sound from the vagina into the uterus. This leads to tKe popular 
delusion that sterility is caused by closure of the mouth of the womb — 
a wholly normal state. In our abattoir observations we incised the 
cervix uteri of over 1,500 nonpregnant cows and heifers and found 
in one only a closure of the cervical canal other than the normal 
approximation related above. 
During estrum the cervical walls relax, the cervical canal dilates, 
and it is frequently possible to introduce a finger or sound into the 
uterine cavity. In severe cases of sterility accompanied by nympho- 
mania the cervical canal is frequently dilated. 
When pregnancy occurs preparations are promptly begun and 
early completed to hermetically seal the uterus. A tough transparent 
gelatinoid substance — the uterine seal— forms in the cervical canal. 
It extends from the external to the internal os; pushes between the 
longitudinal mucous folds, pushing them apart while filling com- 
pletely the spaces between them, fixing each fold in a definite position 
and binding it on either side to the adjacent folds; pushes the sum- 
mits of the mucous ridges apart in the center of the canal, which it 
completely fills; invades and fills the spaces behind the transverse 
valvular folds; and binds and closes in a most intimate manner the 
entire cervical canal. The uterine seal projects beyond the internal 
os into the uterine cavity as a hemispherical elevation and posteriorly 
projects in a similar manner into the vagina, where it may be recog- 
nized by digital palpation as an elastic, adhesive mass adhering to 
the finger tip as it is withdrawn, constituting almost always a valid 
proof of pregnancy. It begins very early after impregnation, and is 
more prompt in heifers than in cows. It is generally complete in the 
heifer when the embryo is one-fourth of an inch long and in the cow 
when the embryo has reached a length of one-half to one inch, though 
