280 
HOT IN SHEEP. 
invariably with the same result, thus showing that the ova of 
the flukes, if introduced into the system of the sheep, will not 
generate or develop into flukes. We find, then, that all these 
theories have been more or less at fault, and it is only within, 
comparatively speaking, a very short space of time, that we 
have approximated to anything like a correct explanation of the 
cause of rot. You will remember that I stated I was anxious 
to confine my remarks entirely to the malady in which we have 
certain entozoa within the biliary ducts. In this diagram 
you have a representation of one of these creatures. It is 
called the JJistoma hepaticum , and is so designated in con¬ 
sequence of its having apparently two mouths or sucking- 
discs—one placed at the anterior part of the body, which may 
be truly regarded as a mouth ; and the other on the ven¬ 
tral surface, at a short distance below the neck, just where it 
terminates in the body. The creature, as 1 have said, inhabits 
the biliary ducts of the liver (which you have represented in 
this diagram); and if we slit up these ducts in any case of 
the kind, we shall find that they are filled more or less to 
* _ f 
repletion with Distonia. Before going into the natural history 
of these creatures, I may now say that after a certain length 
of time they lead to an anaemiated condition of the entire 
organism. They not only feed upon the bile which is pro¬ 
duced, but they alter the structure of the liver by their pre¬ 
sence, just as we find with entozoa in other parts, and when 
this is the case it is of course perfectly impossible for the liver 
to secrete healthy bile, any more than pure water can flow 
from an impure spring. The bile plays an important partin 
the manufacture of blood, and if it is not in a healthy con¬ 
dition pure blood cannot be produced from the food which the 
animal takes. The result is that the entire organism is sup¬ 
plied with impure blood, while the system is being drained by 
the presence of these creatures. After a certain length of 
time we find that dropsical effusions take place, and 
then we have the disease established in all its intensity 
and in all its destructiveness. Having thus shown you 
that this is truly to be considered as an entozoic disease, it 
becomes a matter of great importance to see how these 
entozoa really do inhabit that part of the system of the 
sheep. When speaking of sheep, however, I may be allowed 
to remark that, although this affection is most destructive to 
that animal, it is not exclusively a sheep-disease. These 
creatures have been found not only in cattle but in pigs, in 
the ass, and also in the human subject. They are very widely 
dispersed, but it is in the sheep in particular that they accumu¬ 
late in such numbers as absolutely to produce this special or 
