732 



ARTHROPODA 



sucking. The palpi are three- jointed, and pressed to the under surface of 

 the rostrum. The legs are eight in number, short, and consist of three segments 

 with small terminal ungues. The abdomen is tapering, striated dorsally and 

 ventrally, and rounded at the tip. The anus is situated at the anterior end 

 of the abdomen. 



Demodex folliculorum Simon, 1842. 



Synonyms. — A cams folliculorum Simon, 1842; D . folliculorum Owen, 1843; • 



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

 Steatozoon folliculorum Wilson, 1847. 



This parasite was first discovered by G. Simon, of Berlin, in 1842, in the 

 contents 'of pustules of Acne sebacea. 



About the same time Henle had found them in hair- 

 follicles in the external auditory meatus, and Topping 

 a variety in the dog. Two other species are known: 

 D. phylloides Cook in pigs and D. hovis Stiles in cattle. 

 D. folliculorum hominis is cosmopolitan, living in the 

 sebaceous follicles of the face. 



Male measures 300 ^ by 40 /j,, and the female 380 

 by 45 fj,. 



Life- History. — The eggs are 60 to 90 /a, in length by 

 20 to 50 /J, in breadth, and heart-shaped or fusiform. The 

 egg hatches out a six-legged larva, which develops into 

 an eight-legged nymph, from which the adult appears. 



Pathogenicity. — Usually said to be nil, but a few 

 authorities suspect the parasites to produce acne-like 

 eruptions, and Borrel considers they play a part in the 

 spread of cancer and leprosy. 



ARACHNIDS INGERT.E SEDIS. 

 LiNGUATULIDA. 



Parasitic Arachnoidea with ringed, elongated, 

 vermiform bodies, possessing two pairs of hooks 

 in the neighbourhood of the jawless mouth. 



Remarks." — The Linguatulidahsive been found 

 parasitic in man both in the adult and larval 

 conditions, but the adult is much rarer than the 

 larva. They have been found in Europe and 



Demoiex Africa, and reported from the West Indies, but 



follicHlorytm Simon, this was in a negro from West Africa. It is not 

 1842. (X 150 ) impossible that they will be found to be far 

 (Partly after Berlese.) from uncommon parasites when the medical 

 history of the West Coast of Africa is better 

 known. When dealing with cases showing obscure abdominal or 

 pulmonary symptoms in that part of the world, the medical man 

 should remember these parasites. 



Morphology .—The body is white in colour and vermiform in 

 appearance, and, indeed, they were long mistaken for worms. 



It is elongated, flattened, or cylindrical, and marked by a variable 

 number of rings, and is usually divisible into two regions — an 

 anterior broader portion called the cephalothorax, and a posterior, 

 more attenuated, called the abdomen. It is covered with a chitinous 

 cuticle pierced by pores, called stigmata, which have nothing to 

 do with respiration, being merely the orifices of epidermal glands. 



