appears within the first two or three days after calving, but it has been
known to occur before, and as late as several weeks after calving. The
cause is not certainly known. The Schmidt theory is that certain toxins are
formed in the udder, owing to the over activity of the cells of the
glandular tissue.

[Illustration: FIG. 20.--A case of milk-fever.]

_The symptoms_ are characteristic of the disease. At the very beginning of
the attack the cow stops eating and ruminating, becomes uneasy, switches
the tail, stamps the feet, trembles, staggers when forced to walk and
finally falls and is unable to get up. At first she may lie in a natural
position; later, as the paralytic symptoms become more pronounced, the head
is laid against the side of the body and the animal seems to be in a deep
sleep (Fig. 20). In the more severe form the cow lies on her side,
consciousness is lost and the paralysis of the muscles is marked. The
different body functions are interfered with; the urine is retained,
bloating occurs, respirations are slow, pulse weak and temperature
subnormal or normal.

_Preventive treatment_, such as feeding a spare diet during the latter
period of pregnancy, is not always advisable. Heavy milkers should be given
one-half pound of Glauber's salts a day or two before calving, and the dose
repeated when the cow becomes fresh. Cows affected with milk-fever seldom
die if treated promptly.

The _treatment_ consists in emptying the udder by milking and injecting air
or oxygen gas into the gland until it is completely distended (Fig. 21).
The milk-fever apparatus should be clean, and the air injected filtered.
Before introducing the milking tube into the milk duct, the udder should