DISEASES OF THE SKIN, 461 
The sweat glands of the horse, like those of man, are composed of 
simple tubes, which extend down through the cuticle and dermis in a 
spiral manner, and are coiled into balls in the deeper layer of the 
true skin. In-addition to their importance in throwing offensive 
waste products out of the system, these glands tend to cool the skin 
and the entire economy of the animal through the evaporation of 
their watery secretion. Their activity is therefore a matter of no 
small moment, as besides regulating the animal heat and excreting 
impurities, they influence largely the internal organs through the 
intimate sympathy maintained between them and the skin. 
Diseases of the skin may be conveniently divided, according to 
their most marked features, into— 
(1) Those in which congestion and inflammation are the most 
marked features, varying according to the grade or form into (a) 
congestion with simple redness, dryness, and heat, but no eruption 
(erythema); (b) inflammation with red-pointed elevations, but no 
blisters (papules); (¢) inflammation with fine, conical elevations, 
each surmounted by a minute blister (vesicle); (d) inflammation 
with a similar eruption but with larger blisters, like half a pea and 
upwards (bulle); (e) inflammation with a similar eruption, but 
with a small sac of white, creamy pus on the summit of each eleva- 
tion (pustules); (f) the formation of pustules implicating the super- 
ficial layer of the true skin, a small portion of which dies and ‘is 
thrown off as a slough, or “core” (boils); (¢g) the formation of 
‘round, nodular, transient swellings in the true skin (tubercles) ; and 
(A) the excessive production of scales, or dandruff (scaly or squa- 
mous affections). 
(2) Diseases in which there are only deranged sensations of itch- 
ing, heat, tenderness, etc. . (neurosis). 
(3) Diseased growths, such as warts, callosities, horny growths, 
cancer, etc. 
(4) Diseases from parasites, animal and vegetable. 
(5) Diseases connected with a specific poison, such as horsepox, 
erysipelas, anthrax, farcy, or cutaneous glanders, etc. 
(6) Physical injuries, like wounds, burns, sealds, etc. 
CONGESTION (RED EFFLORESCENCE, OR ERYTHEMA). 
This is a congested or slightly inflamed condition of the skin, unat- 
tended with any eruption. The part is slightly swollen, hot, tender, 
or itchy, and dry, and if the skin is white there is redness. The red- 
ness is effaced by pressure, but reappears instantly when it is re- 
moved. Except in transient cases the hairs are liable to be shed. 
It may be looked on as the first stage of inflammation, and therefore 
when it becomes aggravated it may merge in part or in whole into a 
papular, vesicular, or pustular eruption. 
