Arrangement of Milk Ducts 5 
and is partially separated from the canal of the 
teat by a more or less well-marked constriction 
in the muscular walls of the upper part of the 
teat. From the milk cisterns a system of canals 
or so-called milk ducts extends to all portions of 
the udder. These ducts are larger near their open- 
ing into the milk cistern, and diminish in size 
as they rise through the udder. They branch and 
anastomose freely in all directions, and finally end 
in a group of small sac-like bodies, the ultimate 
follicles. The system of milk ducts arising from 
each teat is practically distinct, though there is 
more or less communication between the smaller 
ducts in the upper portions of the two quarters 
on the same side of the animal. This renders 
it possible to draw a part of the milk secreted 
in the hind quarter from the forward teat on 
the same side, and vice versa. There is no com- 
munication between the ducts on opposite sides 
of the animal. At the junctions of the larger 
ducts there are greater or smaller enlargements, 
forming small cavities or milk reservoirs, which 
serve the same purpose’ as the reservoirs at 
the top of the teat. The branching points of 
all the, ducts, large and small, are guarded by 
sphincter muscles. These muscles are connected 
with the abdominal muscles of the animal, and she 
is able to more or less completely close them at 
will, and so “hold up” her milk. It requires a 
strong effort on the part of the animal to com- 
pletely close the larger ducts in the lower part of 
