DISEASES OP THE SKIN. 321 



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 ascribable to an atrophy, contraction, or hardening of the 

 skin, when the nerves become irritated by the pressure. These con- 

 ditions may be so slightly mai'ked in a thick skin like that of the ox 

 that they can not be recognized. It is frequently noticed that cattle 

 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 one that 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 inflammatory 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 must place our chief reliance upon a change of 

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

 active cathartic — 1 to IJ 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 mixed with the feed may be given 

 twice a day for a week. 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 



ERYTHEMA. 



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

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

 siderable surface. The red coloration disappears when pressed by 

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

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

 glutinous discharge 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 and extend into the 

 corium, or true skin. 



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

 tion, is seen in very young calves, in which the navels leak. The dis- 

 33071°— 16 21 



