344 THE ANIMAL PARASITES OF MAN 



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 

 roundish heap of small cells are seen, from which the entire body of 

 jerks them forward again when required. In the middle of the body a 

 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 utilised. 



Species of acanthocephala only occur exceptionally in human beings. 



I. Echinorhynchus gigas, Goeze, 1782. 

 Syn. : Tcenia hirudinacea, 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 15 cm. in length, the 

 females 30 50 cm. ; the eggs are provided with three shells, of which 

 the middle one is the thickest. The eggs measure 0*08 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 ; occa- 

 sionally 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 

 of l EcJrinorhync1nfs rare - This statement, however, has not been confirmed, 

 gigas. 300/1. (After Its presence in man is by no means impossible, as its 

 Leuckart.) intermediary host, the cankerworm, or cockchafer 



(Melolontha), is, according to Schneider, occasionally 



eaten raw by human beings. According to Kaiser, the golden beetle 

 (Cetonia aurata), and, according to Stiles, another beetle in America (Lach- 

 nosterna arcuata} are also intermediary hosts. 



2. Echinorhynchus hominis, Lambl, 1859. 



This term is applied to an ECHINORHYNCHUS found by Lambl in the 

 intestine of a boy who had died of leuccemia ; the worm was 5 '6 mm. in 

 length, and the almost spherical head was beset with twelve transverse rows 

 of hooks. 



