170 GERLACH ON THE ITCH AND MANGE. 



found by scraping the skin and examining the mass of hairs, 

 exudation, and desquamated cuticle with a fair lens. The 

 Dermatodectes equi, which has hitherto been looked upon as 

 the veritable Sar copies or Acarus equi, does not live, like the 

 latter, on the skin of other creatures besides the horse. Its 

 existence is short, if conveyed to the skin of man, or of an 

 ox, sheep, dog, &c., and the form of horse mange which it 

 induces is, therefore, essentially confined to the equine 

 species. 



Hering first described an acarus which he found in a case 

 of what he believed to be canker of the foot, and he called 

 the parasite Sarcoptes hippopodos. A drawing of this insect 

 will be found in the Veterinarian for 1856. Gerlach 

 designates this epizoon Symbiotes equi, and says that the 

 disease induced by it may be called foot-mange, but it has 

 nothing in common with canker or other known cutaneous 

 eruptions. Attention is first drawn to a horse with this dis- 

 ease by his rubbing his fore-legs, or striking constantly with 

 the hind ones during night-time. The seat of the disease, 

 and the ready detection of numerous parasites in clusters 

 where the crusts or scabs form about the horse's heels, &c., 

 suffice to enable us to diagnose the malady. Mallanders and 

 sallanders Porrigo metacarpi et carpi, metatarsi et tarsi 

 often become associated with this form of mange, which 

 Gerlach terms Scabies equi symbiotica. The Symbiotes equi 

 appears to live only on the horse, and the disease of which 

 it is the cause cannot be induced in the ox, sheep, pig, dog, 

 cat, or rabbit. 



The ox is more rarely affected with mange than the horse. 

 Gerlach says he has found two distinct parasites belonging 

 to the species Dermatodectes and Symbiotes. These are very 

 similar in form to those met with on the horse, but do not 

 live on the latter animal. The parasite which Gohier men- 



