TAPE WOEMS. 61 



accompanies the disease may possibly be due to lymphatic 

 obstruction or inflammation. 



Tape Worms are confined to the intestine, the head being 

 adherent to the mucous membrane. The spaces beneath the 

 valvulse conniventes afford a particularly secure and protected 

 point of attachment. 



The cysticercus stage of Tcenia solium occasionally occurs in 

 man, the eggs having been swallowed or possibly having even 

 reached the stomach by regurgitation when the intestine is 

 inhabited by the mature worm. The hexacanth embryos 

 penetrate the blood-vessels and are carried to the brain, heart, 

 eye, and other parts. The rarity with which they are found in 

 the liver throws doubt upon the carriage by the portal vein. 

 \Vhen found free in the chambers of the eye they have probably 

 escaped from the vessels of the choroid or iris. The presence of 

 the vesicles in the eye, where they can be seen with the ophthal- 

 moscope, and in the skin whence they can be excised for examina- 

 tion, is of assistance in diagnosis. Pressure largely influences the 

 size and form of the vesicles. In the cerebral ventricles where 

 they are free to grow they attain a larger size than elsewhere, 

 attaining the diameter of nearly an inch in some cases. In the 

 subarachnoid space they may assume a flattened dendritic form. 



When the ova of Tcenia echinococcus are ingested by man the 

 six-hooked embryos are set free in the stomach by digestion of 

 their chitinous envelopes, and work their way through the 

 mucous membrane of the stomach into the blood-vessels of its 

 walls. The embryos having been found in the portal vein, it is 

 reasonable to infer that their distribution is mainly effected by 

 this vessel. This would account for the great frequency of 

 hydatid cysts in the liver, and also account for the fact that, 

 next to the liver, the lungs are the commonest site of the disease, 

 for if the embryos succeed in traversing the liver, the normal 

 course of the circulation would carry them through the hepatic 

 veins to the right side of the heart, and thence to the pulmonary 

 capillaries. The parasites which have succeeded in traversing 

 both the hepatic and the pulmonary filters are carried on by the 



