388 



THE ANIMAL PARASITES OF MAN 



DEVELOPMENT. The ova which are found in masses in the 

 nasal mucus already possess an embryo ; they are expelled with 

 the nasal secretion, and are swallowed by herbivorous mammals 

 with their food, mostly by hares and rabbits, but also by sheep, 

 goats, oxen, horses, antelopes, fallow deer, pigs, cats, and occa- 

 sionally also by human beings. The young larvae hatch out in the 

 stomach ; they possess a thickened anterior body with rudimen- 

 tary mouth parts and two pairs of limbs ; the 

 body gradually tapers to a short tail. 



The larvae of the Linguatulidce bore through the 

 intestinal wall and reach the liver, more rarely the 

 mesenteric glands, &c. ; they 

 here become encysted and enter 

 a sort of pupal stage in which 

 they lose their limbs ; after 

 several moultings and gradual 

 growth the second larval stage, 

 having the appearance of the adult 

 Linguatula, sets in. About five 

 to six months after infection 

 the creatures have become 4 6 

 mm. long, possess eighty to 

 ninety rings, which have a series 

 of fine points on their, posterior 

 border ; the mouth and intestine 

 are formed, the sexual organs 

 mature and the two pairs of 

 hooks are near the mouth. 

 This larval stage (fig. 250) has 

 been known for a lon^ time, 

 , but it was regarded as an inde- 



FIG. 249,Lzngua- FIG. 250. Larva of r i 



tula rhinaria, fe- Linguatula rhinaria pendent SpCClCS OI animal, and 



male, natural size. \*^ffi t ^*_ therefore had a separate name 

 kart). Enlarged. (Linguatula serrata, Fr., Penta- 

 stoma denticulatum, Rud., &c.). 



The further course of these Lingvafula-larvst is only peculiar 

 in so far as they make efforts to leave their hosts, and this 

 can only take place by active movements ; they abandon the cysts 

 that harbour them, and according to their situation in the abdominal 

 or pleural cavity, they reach either the bronchi or the intestine, 

 and thence finally reach the open ; here they are sniffed up by 

 dogs, &c., and settle themselves in the nasal cavities. But these 



