208 INTERNAL PARASITES. 



the five-mouths resemble mites, and possess four legs, but 

 when adult no external organs are visible except two pairs 

 of small hooks on the head {Jlf), a mouth (r>), and two 

 minute tactile organs at the anterior border. The hooks 

 can be withdrawn into little sheaths or pockets, which, with 

 the mouth, make five openings in the head, hence the name 

 "Five-mouths." They possess no organs of vision. The 

 sexes are separate; the grayish-white female, 7 to 10mm. 

 long, is very much larger than the white male, -which 

 measures from 2 to 2.5mm. 



The Tapeworm-shaped Five-mouth {Linguatula {Pen- 

 tastoma) kenioides) is illustrated in fig. 172. The female de- 

 posits her eggs, about 500,000, in the nasal cavities of the 

 dog, fox, wolf, and other carnivorous animalls, whence they 

 are expelled with mucus during the fits of sneezing caused 

 by their presence, and in this manner thej^ reach the surface 

 of various low-grov^ing plants or water. Protected by the 

 mucus they keep alive for a number of weeks. If the plants 

 coated with such eggs are eaten by any herbivorous animal, 

 the mucus and egg-shells are dissolved, and the embryos, 

 which were fully formed when the eggs were laid, are liberated 

 in the intestines of the new host. The embryo is flat on the 

 lower, round on the upper surface, and constricted and den- 

 tated at the posterior end. In this larval shape it bores 

 through the walls of the digestive tube by means of a per- 

 forating apparatus formed by a style with two hooks, and 

 thus reaches the liver, lungs, etc., where it becomes encysted. 

 Here it gradually assumes the pupal shape. During the next 

 five months a number of moults take place, and the body of 

 this secondary larva becomes elongated, broader in front, 

 and is divided into SO to 90 segments, which possess a series 

 of fine points on their posterior borders. (Fig. 172). To- 

 wards the seventh month these larvte are completely de- 

 veloped, measuring from 6 to 8mm., and now leave their old 

 home. Most of them die in their attempts to reach the nasal 

 cavities of a new host, but some Succeed. Dogs that eat the 

 viscera of animals containing these parasites are certain to 

 become infested with them. At all events the larvae must 

 reach respiratory organs to complete their growth, which 



