Predisposition. Symptoms. 889 



closing of the glandular brifice or whether the chemical irritation produced by 

 these substances plays a part, cannot be decided from the results of observations 

 that have been made hitherto. 



Acne arises secondarily in acariasis and rarely in the course 

 of strangles in horses, in distemx)er (personal observation) and 

 according to Frohner in bromism. 



Predisposition. Horses and dogs are most inclined to the 

 affection, hogs and sheep only exceptionally. Yonng animals 

 and short-haired dogs appear most frequently to l)e attacked 

 by acne (Sehindelka). 



Symptoms. In horses millet to pea-sized nodules develop 

 on the aforementioned parts of the body (Fig. 126), which are 

 distributed either diffusely (Acne disseminata) or thickly 



Fig. 126. Acne in the horse. 



clustered together and concentrated in groups of nodules (A. 

 confluens). Little vesicles form in the center, the contents of 

 which are first clear and soon after become turbid. Soon after 

 bursting of the vesicles the content dries to a small scab, and 

 mats the enclosed hair. Later on the scabs fall off with the 

 matted hair, whereupon little hairless spots remain for a long 

 time. In some nodules suppuration occurs, and on pressure 

 bloody pus or a thick tallow-like mass may be pressed out from 

 them. After this the swelling disappears in a short time, and 

 the remaining saucer-shaped loss of substance soon heals, leav- 

 ing a light but rather thin-skinned bald place behind (socalled 

 shell nodule) . Many nodules retrogress without previous vesicle 

 formation or suppuration and disappear, leaving no trace be- 

 hind them. 



