138 PAKASITIC SKIN DISEASES. 



of course, reasonable limits. We may put the period at, under 

 ordinary circumstances, from two to ten days. According to 

 Gerlach, the eggs may remain fertile for a month. 



DURATION OF THE DISEASE.— Mange, in both the psoroptic 

 and sarcoptic forms, shows no tendency to spontaneous recovery. 

 The same might be said of symbiotic mange; although it is pos- 

 sible in some cases that this disease may disappear with age, or 

 with ordinary grooming. 



EFFECT ON THE GENERAL HEALTH OF THE HORSE.— 



Sarcoptic mange greatly affects the general health, especially if it 

 be allowed to run its course unchecked, in which case it may not 

 improbably cause death. During the Crimean campaign and the 

 Franco-German war, great numbers of horses died from the effects 

 of this kind of mange, aided by hardships and privation. Psoroptic 

 mange, owing to its slower spread, has not such quickly acting ill- 

 effects ; although it also has a very debilitating influence, which, 

 in neglected cases, may haA^e a fatal result. 



TRANSMISSIBILITY OF MANGE TO OTHER ANIMALS.— As 



the parasites which produce sarcoptic mange (or itch) in, respec- 

 tively, men, horses, dogs, foxes, etc., are varieties of the same insect 

 {sarcoptes scahiei) ; the sarcoptic parasites of one species of animal 

 will, if transferred to the skin of another species, attack it as a 

 rule. In all cases, the occupation seems to be but temporary, pro- 

 bably, not exceeding a month in duration ; although the disease 

 might be kept up by fresh importations of parasites. Among 

 troops, and especially on active service, therei have been several 

 instances, which must, however, be regarded as exceptional, of 

 cavalry soldiers suffering a great deal from the attacks of sarcoptes 

 from mangy horses. On the other hand, the itch insect of man — 

 whether on account of the horse's skin being thicker, or by reason 

 of lack of numbers — is but little formidable to the horse. Hence, 

 there is not much objection to men, who are afflicted with itch, 

 grooming sound-skinned horses : of course, under circumstances of 

 necessity. 



DIAGNOSIS. — The only sign by which we can authoritatively 

 determine the nature of the complaint, is the presence of the para- 

 site. It is much more difficult to do this with the sarcoptic form 

 than with the other two, owing to the burrowing habits of its 

 parasites, and to the fact that it is only about half their length and 

 breadth. In order to find the insect, Neumann advises us to scrape 

 the surface of the affected skin with a knife, through the scarf-skin 



