114 
ON LEECHES. 
It is, then, very probable that the leeches make these wounds 
by gnawing through the buccal membrane, either to feed on the 
tissue or to revive the openings of the bloodvessels and capil- 
laries of this part, and thus cause the blood to flow, on which they 
gorge themselves with unceasing avidity. These wounds, more 
or less multiplied and extended, appear to be excessively painful ; 
but the sufferings which the animal experiences, and which can 
only be conceived by those who have themselves experienced 
them, are still further augmented by the introduction of the ends of 
strands and the beards of barley, a kind of food very common to 
horses in Spain, where it is planted in great quantities. The 
horse also experiences so much difficulty in eating and drinking, 
that he frequently refuses all nourishment. Lastly, a constant 
salivation, to a greater or less extent, which is itself sufficient to 
injure the digestion and weaken the animal, always exists in these 
cases, so that the horse becomes languid, and every day gets 
thinner and weaker. 
One leech only is rarely found in a horse’s mouth. When this 
happens, whether or not it is the effect of chance, that one leech is 
said to be much larger than when there are a greater number ; it is 
also difficult to explain why these reptiles should be smaller in 
proportion to the number there are in the mouth. I have counted 
as many as sixteen in the same horse, and I have seen their size 
varying from the quill of a pigeon’s feather to that of a finger. 
The leeches cannot stay long in any place but the mouth. They 
are apparently able to live some time to fix themselves there, 
nearly about the height of the third molar tooth on either side. 
The orifices of the principal salivary glands and the parotids open 
at this part of the mouth, and the leeches only fix themselves 
there underneath these orifices, and towards the end of the tongue, 
where open the substance of the salivary, maxillary, and sub- 
lingual glands. Their presence in the mouth always excites, by 
the irritation which they cause, an abundant and uninterrupted 
flow of saliva. What ought we to conclude from all these things ] 
First, that the saliva pleases these worms ; secondly, that the 
saliva, unaltered by mixture with the juice of the food, is neces- 
sary to them in order to supply the place of the water in which they 
live in their natural state ; and, lastly, this circumstance serves to 
explain the possibility of their long stay in the mouth, or in the 
nasal cavities, where I have observed they never remain fixed so 
long as they do in the mouth. The leeches that penetrate into the 
nasal cavities not only stay there a very short time, but usually 
detach themselves spontaneously, and do not cause the same 
wounds which they produce on the mucus of the mouth. 
As for those that are swallowed, if they ever can be, with the 
