242 Diseases of the Skin. 
Animal Parasites of the Skin.—These are included 
under the term Dermatozoa, which embraces a great 
variety in the forms of animal life. Their movements 
are directed in the search for suitable breeding-places, as 
well as for their natural, sustenance, and thus a large 
amount of tissue is destroyed, accompanied by severe 
irritation, which induces a form of active inflammation, 
or true dermatitis. We call the disease mange, as es- 
pecially the result of the presence of the acarus, or mange 
insect ; it is, notwithstanding, true inflammation of the 
skin. Contagion plays the essential part, as true mange 
cannot exist without the parasite. It may attack the 
best of animals, but the common subjects are those de- 
bilitated by want of food and necessary care, whose 
hunger leads them to prowl, and ferret out from the 
dirtiest places the wherewith to appease their hunger, and 
there meet with the acari; or it may be in the company 
of infected dogs that the disease is contracted. The 
differences exhibited by various forms of parasitic disease 
in their potency of contagion, depends on the habits of 
the acarus. Infection, as we understand it, is not a term 
of suitability ; the parasite does not become aeriform, 
nor is it, as far as can be ascertained, carried by the air. 
Scabies, or AZange of the Dog, technically known as 
Sarcoptic Scabies, is the analogue of “itch” in mankind, 
and the “scab” of sheep. The producing parasite is 
the Sarcoptes canis, which usually first invades the parts 
least disturbed by the feet of the sufferer ; thus we find 
the back of the neck is the spot where the earliest signs 
may be looked for. From thence it spreads rapidly, as 
the army of acari have multiplied by thousands or even 
millions. Their operations give the subject no rest. He 
loses his appetite, is depressed, puts on a haggard look, 
and is feverish. He is continually scratching, and the 
wildest paroxysms are usually evident after eating, drink- 
ing, or lying in the warmth of a fire. He enjoys being 
scratched by the fingers, and places himself suitably for 
its being continued over the entire body. From this 
point the disease becomes intensified, as every spot, bed, 
&c., frequented by the patient, and also the sufferer’s 
