684 DISEASES OF THE SKIN. 



this is best effected by purgatives, diuretics, and stomachics. 

 Sulphur, internally administered, is also very useful, stimulat- 

 ing the cutaneous glands, and assisting the process of " casting 

 the coat ;" a process with which these eruptions seem to have a 

 close affinity. 



If the tumours become indolent, they require stimulation with 

 iodine or the iodide of mercury. 



Occasionally the pressure of the harness upon these eleva- 

 tions produces a circumscribed form of gangrene of the skin, 

 surrounded by a red circle of inflammatory congestion and sup- 

 puration. After a time, the gangrenous skin assumes a hard, 

 horny, or leathery appearance, adheres firmly to the subcutaneous 

 tissue, is surrounded by an angry-looking suppurating wound, 

 and from the difficulty experienced in its removal, the white 

 gangrenous patch has been called a " sitfast." 



These sitfasts are also seen to arise independently of any pre- 

 vious pimple, and are caused by the pressure of badly fitting harness. 



The centre of the sitfast seems to retain some portion of its 

 vitality, and from its connection with the more perfectly living 

 tissue being to a degree retained, it is not thrown off spon- 

 taneously, as in the case of a more completely gangrenous 

 patch. The circumference of the patch dries, shrivels up, and 

 irritates the surrounding living tissues, which suppurate more 

 or less abundantly. 



Treatment. — Bemoval of the leathery patch by carefully 

 dissecting it out is the only expeditious method of treatment, 

 the wound, so made, to be afterwards treated in the usual 

 way. Some writers recommend blisters and caustics, but 

 they are quite inapplicable, and the only circumstance that 

 admits of the use of a caustic, is where a thin pellicle of the 

 degraded material is not removed with the knife. In such a 

 case the nitrate of silver, carefully applied, is a useful remedy. 



For an account of cutaneous new formations, the reader is 

 referred to the chapters on Tumoues. 



Purimra hcemorrhagicay scarlatina j variola, and other 

 affections which have hitherto been described as diseases of the 

 skin, are mere symptoms of grave pathological conditions of the 

 body, dependent on an alteration of the fluids belonging to a 

 class of blood diseases, which I hope to describe at some future 

 period. 



