DISEASES OF THE SKIN AMONG DOMESTICATED ANIMALS. 
81 
They live only upon the surface of the skin, and feed upon 
the young epidermic cells, destroying the cuticle and the hairs. 
Transferred to human skin the devmatophagus soon perishes , 
causing at most a slight , ephemeral eruption and never the itch. 
Here belong: 
Dermatophagus equi et bovis , causing a local eruption in 
horses and cattle (Fussraude, Steifsraude.) 
Dermatophagus ovis , causing fussraude of sheep. 
Dermatophagus felis , canis et cuniculi , causing ear-itch. 
Thus there occurs in the horse: 
1 . Sarcoptes itch , which may spread over the entire body, 
but is especially common upon head, neck and shoulders. It 
appears as small circumscribed spots, which soon become bald; 
these gradually enlarge and may become very considerable *in 
size. Careful examination reveals small, usually isolated nodules, 
which soon either become vesicular and burst, or allow a thick, 
sticky fluid to transude. After a while they dry up into brown¬ 
ish crusts. There is also an active desquamation of the epider¬ 
mis. Itching is always marked, and the vigorous rubbing and 
scouring causes superficial or deeper lesions of the skin, and 
inflammatory processes of the most varied kinds. 
2. Dermatocoptes itch. This begins on the mane, tail, over 
the larynx, on the flanks, the inner surfaces of the thigh, in short 
on those portions of the body that are protected by long hairs. 
It appears as grouped nodules, from which a sticky fluid trickles, 
which soon dries up into thick, yellowish-brown scales and crusts. 
As a rule the bald affected spots are sharply divided from the 
normal skin. The further changes occur from the rubbing and 
scouring caused by the intense itching. 
3. Dermatophagus itch. This is localized on the legs and is 
seldom seen above the knee. It causes considerable itching, 
especially at night, giving rise to energetic stamping, gnawing 
and rubbing. Finally there occurs desquamation of the epider¬ 
mis, loss of hair, the formation of crusts and thickening of the 
skin. 
But dermatophagus may exist upon the extremities without 
causing any eruption at all (Johne.) 
