TAPE-WORMS. 351 
in the alimentary canal, and the ducts which empty their contents into it; 
but they occur also in the cellular tissue, and in the parenchyma of the most 
closely invested viscera, such as the liver and the brain. They are most 
frequent ine diseased states of the viscera, and they themselves occasion dis- 
ease, or, at all events, annoyance ; but they occur even in healthy states. 
The difficulty of conceiving how they could get into places so obscure, and 
apparently so well protected, and the fact of their never having been found 
alive except in the interior of living animals, caused it for a long time to be 
believed that they were products of spontaneous generation. It has been 
found, however, by actual observation, that most of them either produce ova 
or living young ones, and that many of them have the sexes in different 
individuals.” Some attain to a very large size. 
The Entozoa are true parasites, and cannot assimilate matter for their own 
growth and nourishment unless they receive it from the body of a living 
animal. They have no vestige of breathing apparatus, which shows that 
they must receive their nourishment aerated by the breathing of the animals 
upon which they are parasitic. This supersedes all necessity of a circulating 
system ; and the traces of a nervous one are so very obscure that many nat- 
uralists have doubted its existence. 
The injury which these intestinal worms occasion to the animals upon 
which they live, when their numbers become éxcessive, is well known. As 
is the case with all mysteries, these creatures, more especially those which 
inhabit the human viscera, have led to a great deal of mystification and 
quackery, and nostrums innumerable are recommended to the public; nor 
are there wanting fabricated imitations of some of the more formidable spe- 
cies, usually prepared from the intestines of other animals. The best 
remedy for those inhabiting the human intestines appears to be animal oil, 
mixed with spirits of turpentine. 
This class is divided into two orders, several families, and a great number 
of genera; we shall, however, confine our observations to the genus Tienia, 
of the second order. This group comprises the Tape-worms, which are 
among the most cruel enemies of those animals in which they dwell, as they 
can absorb their nourishment and exhaust their substance. 
The Tape-worm, one of the most stubborn worms which infest the bowels 
of beasts, and also of man, has its name from the broad, flat, ribbon-like 
appearance of each articulation, and of the whole body, which is composed 
of these articulations. Bremser makes two species, — Tenia and Bothry- 
ocephalus, —both of which were formerly united in one species under the 
name of Zventa. One kind of both species appears in the human body ; 
namely, 1. Tienta solium (the Single or Long-limbed Chain-worm), in 
which the organs of generation are found on one side of every articulation. 
