Tlic Rot in Sheep. 
101 
folate. The border is very firm compared with the general 
surface of the body of the distoma, and is chiefly composed of 
two sets of muscular fibres arranged after the manner of an ordi- 
nary sphincter. Muscular fibres also radiate from the centre of 
the sunken part towards the outer edge of the border. The 
whole arrangement is beautifully adapted for the attachment of the 
entozoon to the mucous membrane of the biliary ducts, whereby it 
is enabled to resist the contraction of the ducts to expel it with 
the bile into the intestine. Use, no doubt, is also made of this 
sucker as a kind of focal point in the entozoon's efforts to travel 
onwards into the smaller branches of the ducts to deposit its ova. 
Besides this, an opinion prevails that the organ is employed in 
the act of coition between two distomata, supposing such to be 
necessary for fructifying their ova. We, however, incline to the 
opinion that no such contact does take place, but that the 
entozoon is self-impregnating. 
Digestive System. — This part of the organism of the distoma 
is more simple in its arrangement than many other portions, and 
although it has been described with much minuteness, several of 
these accounts are very far from correct. It commences at the 
bottom of the mouth or oral sucker as a single tube or oesophagus, 
which runs for a short distance directly downwards, and then 
divides into two main intestinal branches (see Jiys. 5 and 6). 
These branches diverge from each other, and in so doing they 
approach the outer borders of the entozoon. This divergence 
is greatest opposite to the ventral sucker, after which the tubes 
again converge a little, and then run in a parallel course towards 
the caudal extremity, where they split up into numerous fine 
divisions. Where their divergence is most, there also the tubes 
are largest, being often pouch-like in their form. Prior to 
their dilatation, they give off from their outer side four or five 
smaller branches, which take somewhat an upward course in this 
the cervical portion of the entozoon and run towards the margin 
of the creature, dividing in their course in an arborescent manner 
into numerous fine canals, to end ultimately in minute cosca 
ififf- 5). 
From below these branches, usually about fifteen others leave 
each parent trunk, also on the outer side, and take a similar 
course, dividing and ending in the same manner. These, how- 
ever, all incline more or less downwards. The parent trunks, 
thus diminished in size, next split up in the way before described. 
A few branches — rarely more than five or six — leave the trunks 
on their inner side, and running a very short distance towards the 
medium line of the distoma, end likewise in a similar manner. 
The situation of the intestinal tubes is about central between the 
dorsal and ventral surfaces of the entozoon, so that they are 
