8 VETERINARY PARASITOLOGY 
their edges, and hence the dressing used should be 
applied beyond the apparent margin. 
The most hopeful sign of recovery is the appearance 
of a smooth crop of fresh hair. 
DISEASES OF THE SKIN CAUSED BY ANIMAL 
PARASITES. 
PSORIC ACARIASIS (MANGE). 
Mange is the name given to that condition of the 
skin produced by the presence of mange-mites, which 
belong to the Acarina. 
It is a very contagious disease, as the parasites can 
leave the host and pass on to another animal with ease. 
The Sarcoptide are small round or oval parasites, 
with a striated cuticle (usually transversely), and the 
majority are barely visible to the naked eye. When 
adult, each possesses four pairs of legs, composed of 
five segments, and terminating in suckers, used in walking 
as prehensile organs, and known as ‘‘ambulacra.”’ They 
are each carried on a stalk, known as the “‘ pedicle.” In 
addition, there is usually a long bristle at the end of each 
terminal segment. The body is short, thick, and non- 
articulated, the head, thorax, and abdomen being united 
together into one piece. The head bears a projection 
known as the “‘rostrum.” This is the buccal organ, and 
is composed of two prominent trophi, the jaws being 
scissor-like in some, and serrated, or even arranged in 
the form of stiff bristles, in others. They have no eyes. 
The males are less numerous and smaller than the 
females. Many varieties bear copulatory suckers on 
their posterior extremities. 
Life-History.—The mange parasites pass their lives 
either on the skin or in burrows made beneath the 
surface. The ovigerous female lays from twenty to 
