DISEASES OF THE SKIN. 665 



The causes of erythema are cold and heat operating alternately 

 on the skin ; wet. friction, dirt, pressure, and constitutional 

 cavises, such as hereditary predisposition, debilitating diseases, 

 plethora, and poverty. There are three forms of erythema 

 described by some writers. An examination of the divisions 

 will at once show the reader that the causes are described as the 

 diseases. Thus, erythema intertrigo is a superficial inflamma- 

 tion of the skin, produced by a chafe, gall, or fret, induced by 

 friction of one part of the skin against the other, by the har- 

 ness, or by the irritation of urinary discharges flowing over the 

 skin, as when an animal is long confined in the slings, when 

 suffering from cystic calculus, or afly cause of non-ability to 

 \irinate properly. Again, erythema paratrimma means er}^hema 

 from pressure, such as saddle-galls ; and erythema chronicum 

 includes cracked heels, and chapped teats of neWly-calved cows 

 and ewes. I refer to this, in order to explain to the reader the 

 various methods adopted in describing skin diseases. 



Erythema, as seen in the horse, may be divided into acute and 

 chronic ; the latter form being that commonly witnessed in 

 long-standing " cracked heels " of horses, where the skin presents 

 upon its surface bran-like, scaly crusts, the limbs swelling more 

 or less at night, and the animal evincing perhaps a slight stiffness 

 in gait when first moved in the morning, but no suppuration. 



An acute form of erythema is often witnessed in prolonged 

 wet weather, involving the limbs to a considerable extent ; some- 

 times all the four legs, arms, thighs, and surface of the abdomen 

 are covered over by patches of superficial inflammation. This 

 disease is generally known under the elegant and euphonious 

 term of " mud-fever." It is caused by the irritation of wet dirt, 

 and, I was going to say, negligent grooming, but a circumstance 

 has just lately come to my knowledge that compels me to 

 hesitate. It will be generally known that the winter of 1871 

 was a very wet one, and consequently mud-fever a very prevalent 

 disease. Speaking one day to a large cab-proprietor and job- 

 master in this city, and casually referring to the prevalence 

 of sore legs from this disease, he informed me that none of his 

 cab-horses were so. affected, whilst his job-horses were all more 

 or less. so. The reasons he gave were that the cab-horses were 

 never groomed at night : that they came in at all times, tlij-ty 



