INTESTINAL WORMS. 165 
body is cylindrical. The sexes are distinct. They are named Thread- 
worms or Round-worms (Nematoidea, from vipa, a thread, and cidos). 
Cuvier makes a distinct order of this division, that of Intestinaua 
cavitatres ; all the remaining entozoa he unites in a second order 
under the name of Intestinaux parenchymateux. OWEN has denoted 
these two principal divisions of Cuvier by the names Sterelmintha 
and Celelmintha'. In our compressed description of the structure 
of the intestinal worms we shall avail ourselves of the names 
which we have explained. 
In the cystic worms, the tape and thorn-headed worms, there 
is neither mouth nor intestinal canal; the nutriment is introduced 
by absorption of the skin. In the thorn-headed worms two parts 
are met with by the side of the sheath of the proboscis, usually of 
a flattened form, and very small anteriorly. These parts, called 
Lemnisci, are, according to Rupo.pHt, subservient to nutrition. 
They contain, according to the description of VoN SIEBOLD, a finely 
granular parenchyma, and are very vascular. 
In the suctorial worms the intestinal canal commences with 
an esophagus, more or less long, which, at its fore part ( pharyna) 
is surrounded by muscular walls. In those that have a sucker at 
the anterior extremity of the body, the oral aperture is situated at 
its bottom. The intestinal canal divides, below the wsophagus, into 
two branches, which have cecal terminations backwards. In many 
species these branches do not subdivide?; frequently they expand at 
their termination. In other species these principal branches give off 
other branches. This is especially the case in the Liver-fluke of 
sheep (Distoma hepaticum), where the branches divide to such a de- 
gree that the whole canal has an arborescent appearance. The oral 
aperture performs also the office of anus; at least the Distomes, 
which are taken alive from the liver, and exposed to air or placed 
in water, reject by the mouth, entirely or in part, the brown fluid 
with which the intestinal canal was filled?. The genus Pentastoma 
or Linguatula, differs from all the other suctorial worms in the 
1 Topp’s Cyclopedia 1. p. 11t. 
2 As in Distoma perlatum NORDMANN, /. cit. Tab. 1x., Distoma rosaceum, ib. Tab. 
vil., Diplostomata found in the vitreous humour of the eye of the Perch, 7b. 
Tab. 11. 111., and in many others. See also MAIJER Beitrdige zur Anatomie der Entozoen. 
Bonn, 1841, 4to. 
3 Comp. E, MEHLIS Observationes anatomice de Distomate hepatico et lanceolato. 
