THE SKIN. 351 



a gradually increasing circle they are sometimes described 

 as non-contagious ringworm or herpes. This disease is 

 subacute ; several rings may be present, and it is difficult 

 to account for their form. "When the vesicles burst their 

 discharge forms a scab. No special methods of treatment 

 are necessary. Herpes is not frequent in cattle. 



Impetigo — Pustular Dermatitis — results from the power- 

 ful irritant action of certain plants, especially upon the 

 delicate skin of calves. It has also been traced to special 

 acrid plants growing in pastures, and has been found to 

 most often affect animals with white legs and muzzles, 

 which parts it usually involves. A crop of pustules forms, 

 and by the bursting and aggregation of these a yellowish 

 scab is formed, which is persistent, and remarkably dis- 

 figures the animal when it involves the muffle, as it is 

 apt to do. Change of pasture, and nitrate of zinc or of 

 mercury ointment, applied to the parts, will generally 

 effect a cure. A cathartic dose will remove the irritant 

 if it has been ingested, from the alimentary canal, for 

 undoubtedly some of these cases are due to disorder of 

 the digestive tracts, though others depend upon direct 

 irritation of the affected parts. 



Ueticaeia — Nettle-rash — Surfeit — is characterised by 

 the sudden appearance of patches of elastic prominences 

 of the skin, which are in a constant state of itchiness, 

 and disappear almost as rapidly as they came. Several 

 forms have been described, according to the size of the 

 swellings and their heat. The most usual form is urti- 

 caria tuherosa. This is sometimes very dangerous, since 

 it may affect the structures of the muzzle and interfere with 

 respiration and ingestion of food. It is vulgarly termed 

 '^ sting e/^ " hlain/' or " singe/' probably on account of 

 the manifest tingling sensation to which it gives rise, and 

 which renders the animal very uneasy. The causes of this 

 disorder are a high surrounding temperature, a rich pas- 

 ture (especially after a run on poor land), also certain 

 constituents of food, and errors in dieting. Manifestly a 

 purgative is indicated in these cases, salines being pre- 

 ferable to others, and sedative agents may be applied 



