494 



PENTASTOMIDA 



4-- 



calcareous degeneration, and Virchow states " dass beim Menschen 

 das Pentastomum am haufigsten von alien Entozoen zu Verwechse- 

 lungen mit echten Tuberkeln Veranlassungen giebt." The larva 



moults several times, 

 and loses its limbs, 

 which seem to have 

 no connexion with 

 the paired hooks in 

 the adult (Fig. 256). 

 The internal organs 

 slowly assume the 

 form they possess in 

 the adult. The larva 

 is at first quite 

 smooth, but as it 

 grows the annula- 

 tions make their ap- 

 pearance, arising in 

 the middle and 

 spreading forward 

 and backward (Fig. 

 259). In this en- 



FIG. 260. Larva of Porocephcdus proboscideus, seen from cysted condition the 



below. Highly magnified. (From Stiles.) 1, Boring, i remains coiled 



anterior end ; 2, first pair of chitinous processes 1 



seen between the forks of the second pair ; 3, ventral up for Some months, 



nerve - ganglion ; 4, alimentary canal; 5, mouth; aoror( K no . tn T p 11P Tj. ar f. 



6 and 7, gland-cells. lllgtOl^eUCkart, 



six in the case of L. 



taenioides, and a somewhat shorter period, according to Stiles, 1 

 in the case of P. proboscideus. 



The frequency of what used to be called Pentastoma denti- 

 culatum ( = the larval form of L. taenioides) in the body of man 

 depends on the familiarity of man with dogs. Klebs and Zaeslin 

 found one larva in 900 and two in 1914 autopsies. Laenger 2 

 found the larva fifteen times in about 400 dissections, once in the 

 mesentery, seven times in the liver, and seven times in the wall 

 of the intestine. After remaining encysted for some time it may 



1 Zeitschr. wiss. Zool. lii., 1891, p. 85. This contains a very full bibliography, 

 of 143 entries. 



2 Centrbl. Bakter, xl., 1906, p. 368 ; v. also Thiroux, C. R. Soc. Biol. lix., 1905, 

 p. 78. 



