774 MIDLAND COUNTIES VETERINARY MEDICAL ASSOCIATION. 
tubes, which run in an extremely tortuous manner within the 
folds of a ligamentous material to the ovaries or female testicles, two 
in number, and in which is formed the first germ or egg from which 
the future foetus springs. 
When the ovum or egg is ripe for impregnation with the seminal 
fluid of the male animal that peculiar condition of the system termed 
sestrum or heat is brought about; the parts at this time becoming 
more vascular and otherwise greatly changed. If access to the male 
is now denied, the ovum is broken up and cast off as effete matter, 
and the quietude of the system is resumed, until the periodical 
recurrence of the same thing—that is, when another ovum is ripe 
for impregnation ; but if access is allowed to the male, and the 
ovum is impregnated and becomes fertilized, it is then seized by the 
fimbriated edges of the Fallopian tubes before mentioned, and 
through them conveyed into the uterus, where it undergoes a series 
of gradual and very beautiful changes, until an exact fac-simile of 
its parents is produced, remaining here, in the natural order of 
tilings, until it becomes fitted to exist apart from its mother. The 
time required to sufficiently mature the young animal for the enjoy¬ 
ment of this separate existence is called the period of utero- 
gestation, and varies in animals of different species. In those we 
are now more especially considering the average period is, in the 
cow, two hundred and eighty, and in the sheep one hundred and 
fifty-four, days. During this period the foetus lives as part and 
parcel of its mother, receiving from her the blood which is necessary 
for its nourishment and growth. When the embryo has made some 
considerable progress in its development, it is found to be sur¬ 
rounded by three membranes, which have been gradually forming 
since the time of conception ; the first one, immediately contiguous 
to the foetus, is called the “amnion,” which secretes a fluid—the 
liquor amnii —in which the foetus floats, thereby being, to a great 
extent, preserved from concussion and injury. The quantity of this 
fluid varies under different circumstances, being generally greater 
in aged animals that have bred many times, and the size of the 
pregnant animal in a great measure depends upon the amount of 
this fluid. 
The middle membrane (which does not entirely surround the 
foetus) is called the allantoid, and is continuous with the urachus, 
a tube coming from the foetal bladder, and one of the constituents 
of the umbilical cord. Into a sac formed by this membrane is 
deposited the urine formed by the foetus during its existence in 
the uterus. 
The external membrane (the chorion) in the cow and the ewe 
presents a totally different appearance to the same membrane in 
the mare. In the former animals it is studded with rose-like 
protuberances called cotyledons, which being attached to corre¬ 
sponding projections from the temporary lining of the uterus form 
the points of connection between the mother and the foetus ; 
whereas in the mare the union is a kind of dovetail one, somewhat re- 
semblingthat between thehorny and sensible laminse in the foot of that 
