24 BUTTER-MAKING. 
The teat is simply a cylindrical-shaped body, with a hollow 
tube extending down through the center of it. At the bot- 
tom of this opening, or at the end of the teat, there is a sphincter 
muscle. This muscle in some circumstances is drawn up very 
tight, while in other instances it is so loose that it will not guard 
the milk from escaping. In case the muscle is so tight that 
the milk can be drawn only with difficulty, it may be relaxed 
a trifle by entering a small, smooth wooden plug. This will 
usually dilate the opening sufficiently, so that the milk may 
be drawn with comparative ease. In some instances this 
muscle is so tight that it is necessary to relax it by the use 
of a sharp knife. This, however, should be done with sur- 
gical skill; otherwise the whole muscle is likely to be so injured 
as to cause the milk to leak away at all times. 
The upper part of this canal in the teat connects with 
what is called the milk-reservoir. The size of this reservoir 
varies in different cows. The average capacity of this milk- 
cistern is about one pint. The opening from this reservoir 
into the teat is also guarded with a muscle. Over this muscle 
the cow has little control. Over the muscle at the lower end 
of the teat the cow has no control whatever. 
Opening into the sides and top of this reservoir is a large 
number of tubes, which are called milk-ducts. These milk- 
ducts extend from the reservoir up into the milk-gland. They 
radiate in all directions, divide and subdivide, so as to form 
a very large number of small tubes. These milk-ducts are 
surrounded with fibrous muscular tissue, nerves, and blood- 
vessels. They are all guarded by a special muscle at the 
junction to the main milk-ducts, from which they radiate. 
These muscles are so intimately connected with the nerves 
and muscular system of the cow that she is able to open and 
close them at will. There are very few cows that are not 
able to hold up their milk during nervous and exciting periods. 
It is a common occurrence for a milker to get only a small 
part of the milk from a cow. This small amount is the portion 
which is present in the teat and milk-reservoir. Some cows 
