ECHINORHYNCHUS G1GAS 477 



and they thus attain the body cavity. Thence a peculiarly constructed apparatus 

 finally conveys the eggs out. This apparatus consists of the uterine bell and vagina, 

 the latter discharging at the posterior extremity of the body. The bell is a muscular 

 canal provided with apertures at both the anterior and posterior extremities. Its 

 interior space is in direct communication with the body cavity, and the anterior 

 orifice takes up all materials floating in the cavity egg-balls, mature and immature 

 eggs and pushes these further backwards. The continuation of the bell lumen is 

 now narrowed by a number of large cells in such a manner that only bodies of a 

 certain form can pass through this tract and attain the uteius ; everything else is 

 conveyed back into the body cavity through the posterior opening of the bell. 



The eggs are already fertilized in the body cavity, and in this position go through 

 their development to the formation of the embryo. Completely developed eggs are 

 surrounded by three shells, and are generally fusiform. The eggs agglomerate 

 in masses in the uterus until they are finally deposited through the vagina and vulva. 

 For the further development, the transmission of the eggs into an intermediary host 

 usually a crustacean or an insect is necessary ; the metamorphosis is very compli- 

 cated ; but this transmission may be very easily effected artificially by feeding suitable 

 crustaceans (Asellus, Gainmarus, etc.) with the eggs of Acanthocephala ; this being 

 the only method of inducing the larva to hatch out so that its structure may be 

 studied. The larva appears in the form of an elongated, somewhat bent body, at the 

 stumpy anterior end of which there is a crown of hooks or spines, whereas the 

 posterior end is pointed. Especial retractors draw in the hook-beset anterior surface, 

 and an elastic cushion beneath them jerks them forward again when required. In 

 the middle of the body a roundish heap of small cells is seen, from which the entire 

 body of the Echinorhynchus originates, even to the cutaneous layer ; the latter is 

 also the larval skin in which the small Echinorhynchus gradually grows. The 

 development of all the organs takes place within the intermediary host, and the 

 parasite only needs to be imported into the terminal host to attain the adult stage after 

 a certain growth. In some cases, however, a second intermediary host is utilized. 



Species of Acanthocephala only occur exceptionally in human beings. 



Echinorhynchus gigas, Goeze, 1782. 

 Syn. : Tcenia hirudinacca, Pallas, 1781. 



The body is elongated, gradually decreasing in thickness towards the back. 

 The rostrum is almost spherical, and is beset with five or six rows of recurved 

 hooks. The males measure 10 to 15 cm. in length, the females 30 to 50 cm.; 

 the eggs are provided with three shells, of which the middle one is the thickest. 

 The eggs measure o - o8 to 01 mm. in length. The GIANT 

 ECHINORHYNCHUS occurs especially in the intestinal canal 

 of the domestic pig ; it is less common in other mammals. 

 It bores deep into the mucous membrane with its rostrum, 

 and causes an annular proliferation around the perforated 

 spot ; occasionally also it causes perforation of the intestine. 



It is doubtful whether the giant Echinorhynchus occurs 

 in man. Leuckart admitted that there were a few positive 

 cases. According to Lindemann, Ech. gigas occurs in 

 human beings in South Russia, and its presence is not rare. 

 This statement, however, has not been confirmed. Its, 



r FlG i- ?^ 8c T~ ^ gg presence in man is by no means impossible, as its inter- 

 of Echtnorhynckus , , . f , ,, , , ., x 



%igas. 300/1. (After mediary host, the cankerworm, or cock-chafer (Melolontha\ 



'Leuckart.) is, according to Schneider, occasionally eaten raw by human 



