DISEASES OF THE SKIN. 335 



Another cause is found in affections of the liver and of the kidneys, 

 when an increase of effete material has to be thrown off by the skin. 

 Morbid materials circulating in the blood may produce a tickling or 

 smarting sensation of the skin in their passage from the blood to the 

 free surface of the skin. Certain irritating substances when eaten 

 may be excreted by the skin, and coming thus in direct contact with 

 the sensory nerves produce itching, or may go further and cause dis- 

 tinct inflammation of the skin. In another class of cases the pruritis 

 may be due to an atrophy, contraction, or hardening of the skin, when 

 the nerves become irritated by the pressure. These conditions may be 

 so slightly marked in a thick skin like that of the ox that they can not 

 be recognized. It is frequently noticed that cattle will rub themselves 

 as soon as they pass from the stable into the open air — changing from 

 a warm to a cold atmosphere. Again, we may find an animal which 

 does all its rubbing in the stall. We may look for lice, but fail to find 

 them. These conditions are generally attributable to high feeding 

 and to too close confinement. They may be associated with inflam- 

 matory irritation or not; certainly we fail to discover any morbid 

 changes in the skin. There is to some extent a delightful sensation 

 produced by rubbing, and it may partly become a habit of pleasure. 



Treatment. — We m.ust place our chief reliance upon a change of 

 food, plenty of exercise, and in most cases the administration of an 

 active cathartic — 1 to 1^ pounds of Epsom salt, a handful of com- 

 mon salt, a tablespoonful of ginger or pepper, mixed with 2 quarts 

 of water, all of which is to be given at one dose. Afterwards half 

 an ounce of hyposulphite of soda may be given twice a day for a 

 week, mixed with the feed. For an external application, when the 

 skin is abraded or thickened from rubbing, a solution of borax. 4 

 ounces to the quart of water, may be used. Carbolic acid, ^ ounce 

 to a quart of water, will give relief in some cases. 



INFLAMMATORY DISEASES OF THE SKIN. 

 EBTTHEMA. 



This is the simplest form of inflammation of the skin. It consists 

 of an increased redness, which may occur in patches on involve con- 

 siderable surface. The red coloration disappears when pressed upon 

 by the finger, but soon returns after the pressure is removed. There 

 is seldom much swelling of the affected part, though often a glu- 

 tinous discharge may be noticed, which dries and mats the hair or 

 forms a thin scale upon the skin. In simple erythema the epidermis 

 alone is affected ; when it becomes chronic, fissures form, which extend 

 into the corium, or true skin. 



Causes. — Simple erythema, consisting of an inflammatory irrita- 

 tion, is witnessed in very young calves, in which the navel leaks. 



