Parasites and Parasitic Diseases of Sheep. 37 
On post-mortem examination the livers show the characteristic 
cysts or else dark-bluish scars where the flukes have been and where 
healing has taken place. The flukes apparentiy die in the liver 
instead of passing out in the spring, as the common liver fluke does. 
The cysts take on the character of abscesses and may be present in 
the lungs and spleen as well as in the liver. Affected livers and other 
organs contain more or less coal-black pigment characteristic of the 
presence of this parasite. The worms may set up peritonitis, and the 
omentum may show black markings. 
Treatment.—No treatment is known for this disease, though the 
use of oleoresin of male fern or kamala is indicated as for the com- 
mon liver fluke. . 
Prevention.—The same measures that are used in the case of the 
common liver fluke (see p. 35) are indicated here. As already noted, 
while we do not know the life history of this fluke, the probabilities 
are that the measures indicated will apply. 
ROUNDWORMS. 
The parasitic roundworms or nematodes are elongated, cylindrical, 
unseemented worms. Some of them may be properly characterized 
as threadlike or hairlike. The body wall is usually rather trans- 
parent, and when the worms are examined with a microscope the 
internal organs are readily seen, usually in the form of a number of 
tubes. The sexes are generally separate and the males are usually 
smaller than the females. In general the females produce large 
numbers of eggs, though sometimes the eggs hatch in the body of the 
female and some roundworms produce embryos without the previous 
formation of an egg with its yolk material and shell. 
Most of the roundworms of sheep reach the animal in which they 
develop to maturity through the direct swallowing of the eggs or 
young worms without passing through part of their development 
in some intermediate host,-as the tapeworms do. In some cases the 
young worms that have hatched in the fields penetrate the skin of the 
host animal, entering the body in this way instead of by the mouth. 
Other worms have an intermediate host and undergo a certain devel- 
opment in this host before getting to the final host. The intermediate 
host harboring the larval worms may be eaten by the final host, thus 
infecting it through the digestive tract, or such intermediate hosts 
as mosquitoes may infect the final host by inoculating it with the 
larval worms which then penetrate the skin. 
Even in the case of direct infection, when eggs or young worms 
are swallowed by the host animal, nematodes which develop to 
maturity in the intestine may not go directly there and develop 
immediately. They may pass through the walls of the digestive 
