43 2 



THE ANIMAL PARASITES OF MAN 



The source of infection is unknown, but according to Balbiani the 

 eggs develop an embryo in water or moist soil, 

 and this embryo may remain alive several years 

 without hatching; the infection of dogs with 

 embryo-containing eggs did not succeed ; an 

 intermediate stage in fishes is conjectured, 

 but still the infection of cattle and horses is 

 unintelligible. 



Family. Strongylidae. 

 Sub-family. Metastrongylinae, Leiper, 1908. 



Buccal capsule absent or 

 slightly developed, vagina elon- 

 gate, uteri convergent 1 and have 

 a simple musculature. Parasitic 

 in the respiratory or circulatory 

 system. Genera : Metastrongy- 

 lus, Synthetocaulus. 



Genus. Metastrongylus, 



Molin, 1861. 



Mouth with six lips, of 

 which the two lateral are the 

 largest. Postero- and postero- 

 external rays 2 of bursa thin, the 

 rest thick. Only the median 

 ray double. Spicules very long 

 and slender, striated. Vulva 

 immediately in front of anus. 

 Eggs contain an embryo when 

 laid. 



FIG. 306. Diocto- 

 phyme gigas, male. 

 Natural size. (After 

 Railliet.) 



FIG. 307. Eggs of 

 Dioctophyme g'gas ; 

 above seen from the 

 flat, below in optical 

 section. 400/1. (After 

 Railliet.) 



Metastrongylus apri, Gmelin, 1789. 



Syn.: Gordius pulmonalis apri, Ebel, 1777; Ascaris apri, Gmelin, 1789; 

 Strongylus sm's, Rud., 1809; Strongylus paradoxus, Mehlis, 1831; Strongylus 

 elongatus, Duj., 1845; Strongylus longevaginatus, Dies., 1851. 



The male measures 12 to 25 mm. in length ; the bursa is bilobed ; 

 there are five rays in each lobe ; the spicules are thin and up to 

 4 mm. in length. The females measure 20 to 50 mm. in length, 

 the anus is close in front of the posterior extremity, which 



1 Convergent : i.e., the uteri are parallel, converging from the anterior part of body to the 

 vagina, which is near the anus, this position being associated with convergence of the uteri. 

 Divergent : Uteri run anterior and posterior, diverging from the vagina, which in this case is 

 near middle of body. 



2 For nomenclature of rays vide p. 449. 



