968 Acarus Mange. 



until 1845, attention having been called a month after his finding to 

 the occurrence of mites in the comedones of man by Heale (1841), and 

 soon after by Simon (1842). In the dog the hair follicle mite was first 

 found by Tulk (1844) ; in the horse by Wilson (1844), and Gros (1845) ; 

 in the cat by Leydig (1859) ; in the pig hy Obermeier and also by Korzil 

 (1878) ; in cattle by Faxon (1878) ; in goats by Niederhaensern'(1881) ; 

 and in ra])l)its bv Pfeiffer (1903). Besides these authors, Miescher 

 (1843), Gruby (1845), Megnin (1877-1892), Csokor (1879) and recently 

 Gmeiner (1908) have investigated the hair follicle mite; the last men- 

 tioned author also elucidated the pathogenesis of the complaint. 



Occurrence. Acariasis is a frequent and obstinate disease 

 of dogs ; it appears to be prevalent all over the world and, ac- 

 cording to Lemke, has hitherto been found to be absent only in 

 Eskimo dogs. Exceptionally it also occurs in cats ; pigs are at- 

 tacked somewhat more frequently, but on the whole rarely and 

 only in certain neighborhoods, but then they fall sick in great 

 numbers. Isolated cases have also been noticed in cattle, goats, 

 horses and rabbits, while in sheep these mites cause no skin 

 changes (Oschaty found acarus mites in the Meibomian glands 

 of sheep). Acariasis has further been noticed in a Sambu stag, 

 in a roebuck, also in field mice, in house mice, bats and rats. In 

 socalled grubs (comedo) of man the mites are also encountered 

 frequently, but generally occasion no special injury. 



Frohner found 2 per cent of acariasis among 70,000 dogs treated in the Berlin 

 clinic. At the Budapest clinic 2% of the dogs attended proved to be affected. 

 In the Vienna clinic 10% of all dogs with skin disease are affected with acariasis. 



According to Stiles acariasis is not rare in cattle in North America, especially 

 in the southern districts where very considerable damage is caused, since only 

 parts of the skin of the attacked animals is suitable for tanning. 



In pigs Csokor and Legram & Eegulato saw an epizootic occurrence of the 

 disease. 



Etiology. The hair follicle mite (bulb mite, Acarus s. 

 Demodex folliculorum) belongs to the order of Acarina, of the 

 class of Arachnoideae as representative of 

 the family Dermatophila (Demodicida). Its 

 body is elongated, lancet-shaped, or like a 

 laurel leaf; at the thorax the three-jointed 

 legs are given off immediately behind one 

 another, on both sides (in the larva three 

 and in the fully developed animal four 

 pairs), while these are absent on the long, 

 conical, cross-striped al)domen, which is ser- 

 rated at the edges. The lyre or horseshoe- 

 shaped head is provided with a movable 

 niorum.' liagni''f.'^''i5o". i-Qstrum, with Upper and lower jaw and also 

 (After Megnin.) with fcclcrs (Fig. 152). The male is smaller 

 than the female; the eggs are oval spindle- 

 shaped, the larvae hatched from the eggs are similar to fully 

 developed mites, but have only three rudimentary pairs of legs 

 and attain their full development after three moultings. 



