664 DISEASES OF THE SKIN. 



in size, and the vesicles are larger than those of eczema ; they 

 do not burst so quickly, and their contents rapidly become 

 milky. A common seat of herpes is the upper lip, constituting 

 what Professor Dick called " crusta labialis ;" occasionally it is 

 seen on the skin surrounding the hoof, and it is then called 

 herpes coronalis, or crown scab. It begins with some heat, and 

 redness, should the skin be white, on a small patch, upon the 

 surface of which the vesicles appear. 



Herpes is found in the mouth, on the mucous membrane of 

 the rectum, vagina, and in the interdigital space of horned cattle, 

 sheep, and pigs ; in the so-called epizootic aphtha, eczema 

 epizootica, and murrain, or foot-and-mouth disease. 



During the prevalence of some epizootic diseases amongst 

 horses, groups of large vesicles form on the face, lips, even within 

 the mouth, and on the mucous membranes. The vesicles are only 

 seen at their outset, because the epithelium retains the fluid ex- 

 uded under it but for a very short time, so that a white spot is left, 

 produced by maceration of the epithelium, or, if this be removed, 

 a shallow excoriation. No crust is formed, owing to the con- 

 stant soaking of the parts in saliva and mucus. 



HERPES CIPtCINATUS, OR VESICULAR RING- WORM. 



There are two forms of ring-worm in the horse — a non-con- 

 tagious form, the herpes circinatus ; and a contagious ring-worm, 

 tinea tondens, or furfaceous herpes, which will be described 

 hereafter. 



Herpes circinatus is an eruption of vesicles upon inflamed 

 patches of skin, which assume a circular form. The circles are 

 of varying size, and sometimes enclose an area of healthy skin. 

 They increase in size by their circumference. 



In very slight attacks the vesicles are very small, and their 

 contents are disposed of by absorption, the eruption terminating 

 by desquamation. 



Causes. — Some disturbance of the digestive functions, or 

 irritation of the respiratory mucous membrane; the eruption 

 being an effort of the system to eliminate some disposition to 

 internal disease. Horses which have been lately imported from 

 Ireland are very subject to this form of herpes ; it seems to 

 depend upon a general disturbance of the system, brought about 

 by the sea voyage. 



