STRUCTURE OF THE SKIN. 435 



ness is effaced by pressure, but reappears instantly when the pressure 

 is removed. Unless in transient cases the hairs are liable to be shed. 

 It may be looked on as the first stage of inflammation, and therefore 

 when it becomes aggravated it may merge in part or in whole into a 

 papular, vesicular, or jiustular eruption. 



Erythema may arise from a variety of causes, and is often named 

 in accordance with its most prominent cause. Thus the chilling, or 

 partial freezing, of a part will give rise to a severe reaction and con- 

 gestion. When snowy or icy streets have been salted this may extend 

 to severe inflammation with vesicles, pustules, or even sloughs of 

 circumscribed portions of the skin of the pastern (chillblain, frost- 

 bite). Heat and burning have a similar effect, and this often comes 

 from exposure to the direct rays of the sun. The skin that does not 

 perspire is the most subject, and hence the ivhite face or white limb 

 of a horse becoming dried by the intensity of the sun's rays often 

 suffers to the exclusion of the rest of the body {white face and foot 

 disease). The febrile state of the general system is also a potent 

 cause, hence the white-skinned horse is rendered the more liable if 

 kept on a heating ration of buckwheat, or even of wheat or maize. 

 Contact of the skin with oil of turpentine or other essential oils, with 

 irritant liquids, vegetable or mineral, with rancid fats, with the acrid 

 secretions of certain animals, like the irritating toad, with pus, sweat, 

 tears, urine, or liquid feces, will produce congestion or even inflam- 

 mation. Chafing is a common cause, and is especially liable to affect 

 the fat horse between the thighs, by the side of the sheath or scrotum, 

 on the inner side of the elbow, or where the harness chafes on the 

 poll, shoulder, back, breastbone, and under the tail. The accumula- 

 tion of sweat and dust between the folds of the skin and on the sur- 

 face of the harness, and the specially acrid character of the sweat in 

 certain horses contribute to chafing or " intertrigo." The heels often 

 become congested, owing to the irritation caused by the short bristly 

 hairs in clipped heels. Again, congestion may occur from friction by 

 halter, harness, or other foreign body under the pastern, or inside the 

 thigh or arm, or by reason of blows from another foot (cutting, inter- 

 fering, overreach). Finally erythema is especially liable to occur in 

 spring when the coat is being shed, and the hair follicles and general 

 surface are exposed and irritable in connection with the dropping of 

 the hairs. 



If due only to a local irritant, congestion will usually disappear 

 when such cause has been removed, but when the feeding or system 

 is at fault these conditions must be first corrected. WhW^ the coat is 

 being shed the susceptibility will continue, and the aim should be to 

 prevent the disease developing and advancing so as to weaken the 

 skin, render the susceptibility permanent, and lay the foundation of 



