understood, that when the young is large in proportion to the diameter of
the pelvic inlet, it is difficult for it to pass through. This occurs when
mothers belonging to a small breed, are impregnated by a sire belonging to
a large breed of animals. It may also occur if the mother is fed too
fattening a ration and not permitted sufficient exercise.

The part of the foetus that presents itself for entrance into the pelvic
cavity and its position are of the greatest importance in giving birth to
the young. Either end of the foetus, or its middle portion may be presented
for entrance. The _anterior_ and _posterior presentations_ may be modified
by the position that the foetus assumes. It may be in a position that
places the back or vertebrae opposite the upper portion of the inlet, or
the floor or sides of the pelvic cavity. These positions may be modified by
the position of one or both limbs, or the head and neck being directed
forwards instead of backwards. In the _transverse presentations_, the back,
or the feet and abdomen of the foetus may present themselves for entrance
to the pelvic cavity. These presentations may show three positions each.
The head may be opposite the upper walls of the inlet, the foetus assuming
a dog-sitting position, or it may lie on either side.

In order to overcome the friction between the foetus and the wall of the
maternal passages, these parts are lubricated by the fluids that escape
from the "water bags." If birth is prolonged and the passages become dry,
birth is retarded. The hair offers some resistance in a posterior
presentation. Young mares that become hysterical have abnormal labor pains
that seem to hold the foetus in the womb instead of expelling it.

CARE OF THE MOTHER AND YOUNG.--Although birth is generally easy in the
different domestic animals, it may be difficult and complicated, and it is
of the greatest economic importance that special attention be given the