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Parasites of Cattle and Sheep. 
Lice. — These parasites, which induce lousiness, pediculosis 
or plithiriasis, are wingless insects. They are permanent para- 
sites, small, but visible to the naked eye, about one-eiglith 
of an inch long, of a dull white or greyish colour, possessed 
of hooklets for holding on and a mouth for pricking. They 
are usually found lying flat on the surface of the skin, and 
though there is no disposition to leave the host, this is often 
effected by rubbing, &c. The pear-shaped eggs or nits become 
attached to the hairs and contain the young living parasites, 
which quickly come to maturity. Lice found on cattle belong 
to either of two families : the Hcematopinus (Fig. 2), which 
sucks the blood of the host, or the Trichodectes (Fig. 3), which 
lives on skin products and dirt. The ox may harbour two 
varieties of the former and one of the latter. Young animals 
are more commonly affected, and one parasite, the Hcemato- 
pinus vituli seems specially to favour sucking calves. Lice 
tend to spread all over the body, and are usually associated 
with a dirty condition of the skin and a low state of flesh. 
The one species by biting, and both by crawling about, 
induce irritation, and consequent attempts on the part of the 
bearers to rub themselves. The coat is thus often broken, and 
sometimes large patches are denuded of hair. 
Treatment . — Due regard for cleanliness, a liberal diet, and 
keeping apart from infested animals and places recently occu- 
pied by them, constitute the preventive treatment. The cure 
