TYPICAL THREADWORMS 



3427 



TRICHINOSIS WORM COILED UP IN HUMAN 

 MUSCLE (enlarged). 



frequently live for several weeks in the water on the lookout for a favorable host. 

 Having come across, and made their way into a Cyclops, they undergo various 

 changes, but only reach in this host a length of about one-twelfth of an inch, their 

 complete development only taking place after the swallowing of the infested Cyclops 



by a fish. Another 



member of the same 



family is the Syn- 



gamus trachealis, 



which owes its 



double name to the 



fact that the males 



and females are 



found in pairs in the 



windpipes of var- 

 ious birds. They 



sometimes occur in 



such numbers that 



the inflammation set up by their blood sucking suffocates their 

 host. The eggs appear to be brought up into the bird's 

 mouth by crowing, or by the choking cough that the presence 

 of their parent causes. They are then swallowed, and pass 

 out through the alimentary canal. As soon as. they have ob- 

 tained sufficient dampness and warmth, they develop in about 

 a week's time into small thread-shaped embryos, with a blunt 

 head and pointed tail. These obtain an entrance into an- 

 other, or the same bird's mouth with the food, and thence 

 pass into the windpipe. 



Perhaps the most dangerous of all human internal para- 

 site worms is Trichina spiralis. In the mature stage these 

 creatures live in the intestines of mammals and birds, where 

 they propagate and gradually perish. The females are about 

 one-eighth of an inch long, and twice the size of the males. 

 In both sexes the mouth lies at the front end of the body, 

 which is its narrowest part; the tail is stumpy, and in the 

 male provided with a pair of short processes. The number 

 of progeny produced by one female may amount to some 

 thousands, and as soon as these are born they make their way 

 into the blood vessels of their host's intestine, where they 

 are carried by the circulation to some more distant part of 

 the body, and ultimately come to a stop in one of the 

 muscles. Here by feeding they grow in a few weeks to four 

 times their original size, and form between the muscular fibers 

 a great cyst or capsule, in the centre of which the worm lies 



coiled up in a spiral. It has not been ascertained how long the creature can remain 

 in this immature state, but certainly for years, and perhaps decades. It can, how- 



TRICHINOSIS WORM, Tri- 

 china spiralis (male 

 enlarged) . 



