LINGUATULA RHINARIA 



525 



sets in. About five to six months after infection the creatures have 

 become 4 to 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. 372) has been 

 known for a long time, but it was regarded as an independent species 

 of animal, and therefore had a separate name (Linguatula sermta, 

 FT. ; Pentastoma denticnlatuiu, Rud., etc.). 



Later these Linguatula larvae make an attempt to escape from their 

 hosts, and this, of course, can only be effected by means of an active 

 migration ; they leave the cysts, and according to their respective 

 positions in the abdominal or pleural cavities they reach the bronchi 



FIG. 373. Linguatula rhinaria: on left, eggs in gelatinous covering, no/i. 

 On right, first larval stage. 300/1. (After M. Koch.) 



or the intestine, and finally pass out ; they may be again sniffed up 

 by dogs and settle in their nasal cavities. Still this outward migra- 

 tion does not appear to be necessary for further development. A 

 portion of the larvae gain access to the nasal cavities directly through 

 the trachea, and thus herbivorous mammals certainly become directly 

 infected. In most cases the infection of dogs, wolves and foxes, that 

 is, of carnivorous mammals, takes place through consuming the 

 bodies of mammals, or parts of them, such as the liver and 

 lungs, which are affected with the second larval form ; in any case 

 most larvae obtain access first to the stomach of their host, from 

 here they make an. active migration through the oesophagus to the 

 oral and nasal cavities, in which they settle. It is possible also that 



