MUSEUM OF COMPARATIVE ZOOLOGY. 15 



gives an account of the structure and mode of life of the parasite of 

 the hair-follicles.* 



In 1859 appeared a valuable paper on Demodex by Leydig,t contain- 

 ing descriptions of the parasite found on man, the cat, the dog, and a bat 

 from Surinam (^Phyllostoma). On the latter hundreds of specimens were 

 found in a pustule on the belly. He considera the forms from the 

 various hosts as so many species. 



The most important contribution to the history of Demodex since 

 18G0 is a memoir by Megnin.| In this memoir are described three 

 varieties from man, the cat, and the dog. 



In the above-mentioned papers Demodex has figured as a parasite of 

 man, the cat, the dog, the fox, the bat, the ox, and the horse. It has 

 also been reported from the Meibomian glands of the sheep. § 



While in the human skin it is seldom found except in the face and 

 is comparatively innocent, in the dog it may become widely spread over 

 the body, and be the cause of a serious disease accompanied by a loss 

 of the hair in the infected parts. 



Although noticed in the ox by Gros, as long ago as 1845, || it has 

 never been known, as far as I can learn, to induce any serious dermal 

 disorder in that animal. Gros simply mentions it as found in the 

 muffle. Its presence in such numbers as to damage the leather made 

 of the infested skins must from its economic bearings awaken a fresh 

 interest in this peculiar Arachnid. All the samples which I received 

 had been soaked in lime in order to remove the hair, so that I cannot 

 say whether the presence of the parasite causes the hair to fall off as 

 happens with the dog ; but at all events no crusts were formed upon 

 the skin as in the mange. It is probable that the parasites would not 

 have got such a hold upon the cattle unless their skins had become 

 torpid by ill keeping. 



It may be useful to quote here the treatment recommended by 

 Simonds for dogs afflicted with these parasites, as it will apply equally 

 well to cattle : — 



* "Die in und an dem Korper des lebenden Menschen vorkommenden Parasiten," 

 1855. English translation by Edwin Lankester, Vol. II. pp. 15-19, PI. VIII. Figs. 14-16, 

 1857. 



t "Ueber Haarsackmilben und Kratzmilben." Arch. f. Naturgeschichte, 1859, I. pp. 

 338-347, PI. XIII. Figs. 4-10. 



X " Memoire sur le Demodex fnlliciilorum, Owen." Journal de I'Anatomie et de la 

 Physiologic (Robin et Pouchet), 1877, pp. 97-122, PI. IX. 



§ Kiidienmoister, op. cit. (Eng. trans.), II. p. 17. Megnin, op. cit., p. 105. 



II The record of this has been overlooked by most of the recent writers on the subject, 

 e. g. Simonds and Megnin. 



