202 FLAT WORMS. 



INFECTIONS. 



Taenia saginata. This very widely distributed tape-worm is often 

 termed the unarmed tape-worm, to distinguish it from the T. solium or 

 armed tape-worm. It is from 10 to 25 feet long and has several hun- 

 dred proglottides. The small pear-shaped head has 4 pigmented 

 elliptical suckers and no hooklets. The segments are plumper than 

 those of T. solium, hence the name saginata. The single lateral 

 genital pore projects markedly and in a series of segments presents, as 

 a rule, first on one side, and then on the opposite side of the next seg- 

 ment (alternating). The best way to distinguish a segment of the T. 

 saginata from the T. solium is by counting the number of lateral 

 uterine branches; these number 15 to 30 and branch dichotomously. 

 The lateral divisions of the uterus of the T. solium are tree-like in their 

 blanching and only number 5 to 12 on each side. The ox is the in- 

 termediate host. The 6-hooked embryo, having worked its way from 

 the alimentary canal to the muscles or liver of the ox, become encysted 

 (Cysticercus bovis). This little bladder-like structure is about 1/4 by 

 i / 3 inches. Being ingested by man's eating raw or imperfectly cooked 

 meat, the adult stage becomes established in his alimentary canal. 

 In Abyssinia the infection is said to be universal, and a man without a 

 tape worm to be a freak. An important point is the fact that the 

 larval stage never appears in man. It is this fact which makes it a so 

 much less dangerous parasite than the T. solium, which readily es- 

 tablishes a larval existence in man if the ova are introduced into the 

 human stomach. Cooking meat always destroys the Cysticercus. 

 A period of about 2 months elapses after the ingestion of the Cysticer- 

 cus before the mature segments pass out of the rectum. These not 

 only make their exit with the faeces, but are also capable of wandering 

 out at other times. In this they differ from the segments of T. solium. 

 T. saginata next to H. nana is the common tape-worm of the United 

 States. Dr. Stiles has examined several hundred tape-worms during 

 the past few years and has found only one T. solium. 



Taenia solium. The measly -pork tape-worm is smaller than the 

 T. saginata and differs from it in having a globular head, with a rostel- 

 lum, which is crowned by 26 to 28 hooklets. The segments have 

 only 5 to 10 branches and are expelled only at the time of defecation. 



