ON LEECHES. 
113 
selves is so great, that, whatever exertions the horse may make to 
get rid of them, I doubt whether he could ever effect it without aid; 
at least, 1 do not know an example to the contrary. What is still 
more is, that these worms, once established in a horse’s mouth, 
never seem inclined to quit it of their own accord ; and I do not 
think that there is one single case in which they have detached 
themselves or abandoned their refuge spontaneously. 
The leeches, once introduced and fixed in the mouth of a horse, 
gorge themselves almost constantly with blood, but spit it up 
nearly as constantly, because they are incessantly constrained, 
annoyed, or compressed and kept in action by the motions of the 
lips, the tongue, the jaws, the food, and the bit whether of the 
bridle or reins ; therefore they throw off the blood incessantly, 
more or less pure, and in greater or less quantities, which are 
sometimes swallowed as quickly as they furnish it. 
When a horse has leeches in his mouth, he either shews a per- 
fect disgust or a great difficulty in taking and chewing his food. 
When these causes do not simultaneously contribute to make him 
refuse solid food, then, if he is not bridled, whether he eats or 
not, the blood thrown up by the leeches is swallowed by the horse, 
and without examining the mouth the existence of the leeches is 
not apparent ; but, on the contrary, when he is bridled, when the 
motions of the jaws are impeded by the pressure of the headband, 
and that of the tongue by the bit, then the blood cannot be so 
easily got rid of as before. It runs out on both sides of the mouth, 
on the lips, the chin, and the bridle ; and it is commonly by this 
last sign that we are apprised of the existence of leeches in the 
mouth. 
I have said that leeches, in order to fix themselves in the mouth, 
introduce their teeth into the softest and most delicate parts. These 
are under the tongue and near and above the bit, on the inside 
of the lips, a little above their commissure, on the inside of the 
cheeks : but I never saw these reptiles fix themselves and remain 
on the back part of the mouth, where it appears, from some cause 
unknown to me, they cannot remain so long as in the cavity of the 
mouth. 
This introduction of the teeth of the leeches into parts so sensi- 
ble as those which I have mentioned is very painful to the horse ; 
but that is far from being the only evil which these worms may 
cause. For, prolonging their residence in this place, they either 
produce, or cause and extend, every day more and more, and that 
doubtless by incessant gnawing nearer and nearer to that part of 
the mucous membrane on which they are fixed, wounds or fur- 
rows, usually about from three to five millimetres, and which be- 
come larger the longer the leeches remain in the mouth. 
