114 ANIMAL PHYSIOLOGY. 
The ovum in the fowl is fertilized in the upper part of the 
oviduct; in the mammal mostly in this region also, as is shown 
by the site of the embryos in those groups of animals with a 
two-horned uterus, and the occasional occurrence of tubal preg- 
nancy in woman. But this is not, in the human subject at 
least, invariably the site of impregnation. After the ovum has 
been set free, as above described, it is conveyed into the ovi- 
duct (Fallopian tube), though exactly how is still a matter of 
dispute: some holding that the current produced by the action 
of the ciliated cells of the Fallopian tube suffices; others that 
the ovum is grasped by the fimbriated extremity of the tube as 
part of a co-ordinated act. It is likely, as in so many other 
instances, that both views are correct but partial; that is to 
say, both these methods are employed. The columnar ciliated 
cells, lining the oviduct, act so as to produce a current in the 
direction of the uterus, thus assisting the ovum in its passage 
toward its final resting place. 
Menstruation As a part of the general activity occurring 
at this time, the uterus manifests certain changes, chiefly in 
its internal mucous lining, in which thickening and increased 
Fie. 135.—Diagram of the human uterus just Fic, 136.—Uterus after menstruation has just 
’ before menstruation. The shaded por- ceased. The cavity of the body of the 
tion represents the mucous membrane * uterus is supposed to have been deprived 
(Hart and Barbour, after J. Williams). of mucous membrane (J. Williams), 
vascularity are prominent. A flow of blood from the uterus 
in the form of a gentle oozing follows; and as the superficial 
