timated at several hundred.
The time from the eating of the flesh containing the muscle trichinae to
the development of the brood of embryos in the intestines (bowels) is from
seven to nine days. The female worm penetrates the intestinal wall and the
embryos are probably discharged into the lymph spaces, thence into the
venous system, and by the blood stream to the muscles, which constitutes
their seat of election. After a preliminary migration in the
inter-muscular connective tissue, they penetrate the primitive muscle-
fibres and in about two weeks develop into the full grown muscle form. In
this process interstitial inflammation of the muscle is excited, and
gradually an ovoid capsule develops about the parasite. Two, and
occasionally three or four, worms may be seen within a single capsule.
This process of encapsulation has been estimated to take about six weeks.
Within the muscles the parasites do not undergo further development.
Gradually the capsule becomes thicker and ultimately lime salts are
deposited within it. This change may take place in man within four or five
months. The trichinae may live within the muscles for an indefinite
period. They have been found alive and capable of developing as late as
twenty or twenty-five years after their entrance into the system. These
calcified capsules appear as white specks in the muscles. In many
instances however these worms are completely calcified. In the hog the
trichinae cause few if any symptoms. An animal, the muscles of which are
swarming with living trichinae, may be well nourished and healthy looking.
An important point also is the fact that in the hog the capsule does not
readily become calcified, so that the parasites are not visible as in the
human muscles.

Modes of Infection.--The danger of infection depends entirely upon the
mode of preparation of the flesh. Thorough cooking, so that all parts of
the meat reach the boiling point, destroys the parasites; but, in larger
joints, the central portions are not often raised to this temperature. The
frequency of the disease in different countries depends largely upon the
habits of the people in the preparation of pork. In North Germany, where
raw ham and wurst are freely eaten, the greatest number of instances have
occurred. In South Germany, France, and England cases are rare. Salting
and smoking the flesh are not always sufficient, and the Havre experiments
showed that animals are readily infected when fed wit