422 



skin. Tn addition to their importance in throwing offensive wa.:;te pro- 

 ducts out of the system, these glands tend to cool the skin and the en- 

 tire economy of the animal through the evaporation of their watery 

 secretion. Their activity is therefore a matter of no small moment, as 

 beside regulating the animal heat and excreting impurities, it influ- 

 ences largely the internal organs through the intimate sympathy main- 

 tained 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); [h), in- 

 flammation with red pointed elevations but no blisters {papules); (c), in- 

 flammation with fine conical elevations, each surmounted by a minute 

 blister [vesicle) ; [d), inflammation with a similar eruption but with 

 larger blisters, like half a ji^a and upwards (bullse) ; [e), inflammation 

 with a similar eruption but with a small sack of white creamy pus on 

 the summit of each elevation [pustitles) ; (/), the formation of pustules 

 implicating the superficial layer of the true skin, a small portion of 

 which dies and is thrown off as a slough or " core" [boils) ; [g), the for- 

 mation of round, nodular, transient swellings in the true skin [tubercles) 

 and [h), the excessive production of scales or dandruff (sea??/ or squamous 

 afl^ections. 



(2) Diseases in which there is only deranged sensations, of itching, 

 heat, tenderness, etc. [Neurosis). 



(3) Diseased growths, as warts, callosities, horny growths, cancer, etc. 



(4) Diseases due to parasites, animal and vegetable. 



(5) Diseases connected with a specific jjoison — horsepox, erysipelas, 

 anthrax, farcy or cutaneous glanders, etc. 



(6) Physical injuries like wounds, burns, scalds, etc. 



CONGESTION — RED EFFLORESCENCE — ERYTHEMA. 



This is a congested or slightly inflamed condition of the skin, unat- 

 tended by any eruption. The part is slightly swollen, hot, tender or 

 itchy, and dry, and if the skin is white there is redness. The redness 

 is effaced by pressure, but reappears instantly when the pressure is re- 

 moved. Unless in transient cases the hairs are liable to be shed. It 

 maybe 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. 



Erythema may arise from a variety of causes, and is often named in 

 accordance with its most prominent cause. Thus the chilling ot \y.vA\\\\ 

 freezing of a part will give rise to a severe reaction and congestion. 

 Where snowy or icy streets have been salted this may extend to severe 

 inflammation with vesicles, pustules, or even sloughs of circumscribed 

 portions of the skin of the pastern (chill-blain, frost-bite). Heat and 



