3 86 



THE ANIMAL PARASITES OF MAN 



small terminal ungues. The anus is situated on the anterior border of 

 the abdomen ; oviparous ; the larvae have six stumpy legs. These mites 

 live in the hair follicles of mammals. 



Demodex folliculorum (Simon), 1842. 



Syn : Acarus folliculorum, Sim, 1843; Dem. folliculorum, Owen, 1843; 

 Macrogaster platypus, Miescher, 1843; Simonea folliculorum, P. Gervais, 1844; 

 Steatozoon foil., Wilson, 1847. 



As in Sar copies scabiei, numerous varieties of this species are 

 known ; the form parasitic on man lives in the 

 hair follicles, the meibomian and sebaceous glands, 

 and hardly e.ver causes inconvenience ; the male 

 measures 0*3 mm. in length, and the female about 

 0*4 mm. in length. The eggs 0*06 0*08 in length, 

 0*04 0*05 in breadth, and are thin-shelled. The 

 creatures are always attached with the head-end 

 downwards in the parts mentioned ; they are most 

 frequent in the sebaceous glands of the face, 

 by the nose, lips and forehead, but they may 

 be present on the abdomen and on other parts of 

 the body. They may occasionally obstruct the 

 excretory gland ducts, thus causing inflammation 

 of the gland (comedones) ; their agglomeration in 

 the meibomian glands sets up inflammation of 

 the margins of the eyelids. There are generally 

 only a few specimens in a gland. According to 

 some statements Demodex occurs in 50 per cent, 

 of mankind and even in children ; they survive 

 the death of their hosts by several days. 



The variety living in the dog (Dem. folliculorum, var. cam's) is smaller than 

 the variety living in man, and produces a skin disease resembling scabies 

 in these animals. According to Ziirn they may also live on man ; 

 nevertheless, no other investigator has recorded a similar observation, 

 and attempts at artificial infection have proved negative. 1 



Simon, G., " Sur les acares vivant dans les follicules pileux de I'homme " (Arch, 

 de medec. comp., 1843, i., p. 45); Leydig, F., " Ueb. Haarsackmilben u. Kriitzmilben " 

 (Arch. f. Naturg., 1859, xxv., p. 338)"; Landois, L., " Ueb. d. Haarbalgparas. d. Men- 

 schen" (Greifswald. med. Beitr., 1863, L, p. 17); Stieda, L., " Ueb. d. York. d. Haar- 

 balgparas. an den Augenlidern" (Centralbl. f. prakt. Augenhlkde., 1890, July, p. 193) ; 

 Thudichum, J. S. W., " On the Dem. foil, as the Par. Caus. of the Mange of Dog and 

 its Transfer upon Man ",(Med. Press and Circ., 1894, p. 103); Majochi, D., "Int. al 

 Dem. foil, nelle ghiand. meib.," Bologna, 1897 ( /. B., P. u. I., xxv., p. 784); Ivers, 

 K., " Demod. s. Ac. foil. u. seine Bez. z. Lidrandentzdg." (D. med. Wochschr., 1899, 

 p. 220); Raehlmann, E., " Ueb. Blepharitis acarica " (Kl. Monatsb. f. Augenhlkde., 

 1899, xxxvii., p. 33, ref. in C. /. B., P. u. I., xxvi., p. 40). 



1 [This mite causes what we know in England as Red Mange in dogs. F. V. T.] 



FIG. 248. Demo- 

 dex folliculorum of 

 the dog. (After 

 Megnin.) 



