DISEASES OF THE SKIN. 713 



alesce ; until at length such a region as the face presents only one 

 large crust covering the skin, which is indurated, wrinkled, 

 cracked, ulcerated, and bleeding. 



"At this advanced stage, respiration, vision, and even the 

 prehension of food, may be obstructed by the thickness and size 

 of the crusts, and the tumefaction existing around the natural 

 openings. A fatal termination has not, however, according to 

 lieynal, been noted." 



1 am satisfied of having seen one case that was on the point 

 of death from starvation and inability to breathe, arising from 

 the lips and nostrils being indurated and scabbed, and in which the 

 parasites were discovered. The symbiotic, like that in the horse, 

 attacks the legs, spreads but slowly, and is not very contagious. 



Treatment. — The first essential is the separation of the healthy 

 from the unhealthy stock, and, as a precautionary measure, the 

 healthy sheep should be dipped with any of the reputed dress- 

 ings. A very effectual one is a preparation of arsenic (one 

 pound to twenty gallons of water) rendered soluble by the 

 addition of an equal quantity of an alkali ; for example, the 

 carbonate of potash. Sheep should be dipped in dry weather, 

 and penned for the night after the operation, to prevent them 

 eating the drippings from the wool along with their food.' 

 The affected stock must be dressed individually; the wool 

 being first clipped from the margin of the scabbed part (as 

 there the parasites are located), and the part then dressed 

 with tobacco juice, mercurial ointment, spirit of tar, or sulphur 

 ointment. As a dip, carbolic acid is very good, but it has 

 this disadvantage, that it destroys the colour of the wool. 

 The flockmaster must remember that, though he may have de- 

 stroyed the parasite, the ova yet remain, and therefore careful 

 watching is necessary, and a second or even a third application 

 - of the dressing may be required. 



This disease is included in the Contagious Diseases Act, 1869. 



The dermatodectes ovis is moderately hard ; the male is 

 roundish, the female more ovaL Each of the external posterior 

 feet has two long bristles ; the fourth pair of feet in the male is 

 imdimentary. The homy framework of the feet is reddish 

 brown. In order that the reader may compare the delineations, 

 of Gerlach and those of Kuchenmeister, I have inserted the 

 folio wins cuts : — 



