55 
Gr 
ON ENTOZOA. 
intestine towards its origin, do sometimes ascend into the 
stomach, or descend into the large intestines. They have 
even been known to penetrate into the peritoneal cavity, after 
having perforated the intestine, or taken advantage of some 
previous perforation which had been made there. 
The nutriment of the worms is generally animal, and in a 
fluid state, as may be supposed from the formation of their 
buccal orifice. Among the external worms it would seem 
that there are some exceptions to this rule ; but with such we 
have but little to do in the present place. 
The mode in which this nutriment is taken is very simple, 
since in general it is drawn in by the successive action of the 
parietes of the intestine, performing the office of a sucking 
pump. ‘This is quite obvious in the medicinal leeches, which 
are so analogous in structure to the animals of which we are 
now more particularly treating, and the like probably also 
takes place with the ascarides. But in these last, nutrition 
must also take place by the action of the skin, plunged in the 
mucous or chyleous matter, which lines or fills the intestinal 
canal which they inhabit. As for the porocephali, the echi- 
nocephali, and particularly the bothryocephali, and ligule, it 
is clearly evident that they can have no other mode of nutri- 
tion, the intestinal canal being no longer existent in them, or 
being reduced to a merely vascular state. All the nutriment 
is taken by the action of the suckers of the oral extremity, or 
by those of each ring as in the teenie, the bothryocephali, and 
lastly, by the pores of the skin alone, as must necessarily 
take place in the ligule. 
In those in which the sexes are distinct, as in all the asca- 
rides, it is certain that the males are always obviously less 
common than the females, and, most undoubtedly, must be 
considerably less numerous. ‘There are even some species in 
which it is very rare to find any, as in the ascarides, properly 
so called. There are more in the strongyli. 
