918 GANGRENOUS DERMATITIS. 



The experiments of Siedamgrotzky and Jelkmann showed that the 

 lowering of temperature, consequent on the use of salt (which is 

 particularly common in large towns), could not be held responsible 

 for the production of the disease. And, finally, it should be noted 

 that at times, when gangrenous dermatitis is common, all wounds 

 show a tendency to necrosis. It, therefore, seems tolerably clear 

 that local freezing is not the only cause, but that other factors, partly 

 of an infectious, partly of a chemical character, are also at work. 

 Slight injuries to the lower portions of the limb lead to infection, 

 which may result in inflammation and necrosis. Low temperatures 

 depress the vitality of exisiting wound surfaces and thus favour 

 septic invasion. Whatever view may finally prove correct, thus 

 much is certain, that as a rule infection acts along with cold in giving 

 the first impulse to the production of gangrenous dematit is. The 

 cases seen about the coronet and front of the pastern are often 

 initiated by " treads " ; the horse injuring the skin with the calkin 

 of the opposite shoe, and the wound becoming infected. That this 

 form of dermatitis does occur, in exceptional instances, even in the 

 warm season, only shows that necrosis of the skin may be produced 

 independently of cold. 



Symptoms and course. The disease appears suddenly, generally 

 overnight. There is lameness in one or other limb, with inflammatory 

 swelling of its lower portions, sometimes also of the upper parts. 

 Fever is also common. Closer examination detects at a given spot 

 a portion of skin, from 1 to 2 inches in diameter, which is soft, yielding 

 and swollen : pressure over this spot causes severe pain, and produces 

 discharge of a reddish turbid fluid. The pastern is the most common 

 seat of disease, at a point just over the bulb of the heel, or on the 

 anterior surface of the coronet. The pain continues, the limb 

 increases in size, and in two to three days the necrotic portion of the 

 skin is cast off as a soft, grey, slimy mass : the resulting wound then 

 becomes covered with granulations, which gradually fill up the cavity. 

 In favourable cases a cicatrix forms, and recovery is complete in one 

 to two weeks. 



But the disease does not always take so favourable a course ; 

 sometimes the infective inflammation extends downwards to the 

 lateral cartilage, or the coronet bone, or penetrates to the sheath 

 of the flexor tendon. In the first case a quittor forms, in the second 

 an exostosis, which later becomes a ring-bone. And if in such cases 

 suitable treatment often leads to recovery, i.e., to removal of 

 lameness, yet when the coronary vessels, or the sheath of the tendon 

 is also attacked, death may occur in a short time from septicaemia. 



