i PARASITES OF ANIMALS. 113 
The females are larger and more numerous than the males, 
and become about one-eighth ofan inch long when full grown. 
They pair as soon as mature, and the males soon die; 
but the females begin to give birth to living young in five 
or six days from the time when they enter the stomach, 
and they live long enough to produce a brood of from five hun- 
dred to one thousand young worms each. As one ounce of pork 
sometimes contains a quarter of a million or more of the worms, 
it is not surprising that the millions of adult worms and their 
offspring, sometimes resulting from a single meal of raw 
pork, should, by their presence, produce great irritation and 
inflammation of the intestine and violent diarrhoea and vomit- 
ing, which are often the first symptoms in severe cases. But 
the young worms, almost as soon as born, begin to eat or 
force their way through the membranes of the intestine into 
the minute blood-vessels and other organs, thus vastly in- 
creasing the irritation. Entering the circulation they 
are carried by the blood to the heart, thence to the lungs, 
and then become diffused through the whole system. Accord- 
ing to other observers, the young worms force their way di- 
rectly through the intestine and all other intervening organs, 
until they finally reach a suitable habitation in the voluntary 
muscles. It is, however, difficult to understand how they can 
become so evenly and generally distributed through the whole 
muscular system as they often are, if this be their only mode 
of diffusing themselves. Itis, therefore, not improbable that 
they migrate by both these methods, part entering the circu- 
lation and part going directly through the tissues, while in 
either case, if they find themselves in an unfavorable locality, 
they have the power of changing their position while still in 
the free state. According to Dr. Leuckart, they travel by the 
way of the intermuscular connective tissues, and are found 
most abundantly in the groups of muscles nearest the abdomi- 
nal cavity, especially in those that are smallest and have the 
‘most connective tissue. 
Effects. 
Large numbers often lodge in the heart, lungs, and various 
other organs, producing great irritation and various danger- 
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