PARASITES OF THE ALIMENTARY TRACT 51 
It has an elongated body, flat on the ventral surface: 
and rounded on the dorsal surface. The mouth carries 
a tri-radiate, three-lipped sucker, used both for the 
purposes of assimilation and locomotion, and there is 
an anal sucker in the form of a flattened disc. The 
oval sucker is soft, and so the horse-leech is unable to 
attach itself, except to an abraded surface or a mucous 
membrane. 
The Hirudo medicinalis, on the other hand, has hard 
jaws, and is able to puncture sound skin. Although the 
leeches are hermaphrodite, a pair are necessary for fer- 
tilization, the penis being situated at the anterior end 
of the body, and the vulva a short distance behind it. 
The horse-leech frequents muddy pools, and the 
young parasites enter the pharynx of horses, asses, 
mules, or even man. During the process of drinking 
they become attached to the mucous membranes, from 
which they suck blood. 
Symptoms.—When the leeches are present in great 
numbers anemia and debility arise from loss of blood. 
The patient frequently coughs, and such attempts to 
remove the parasites are followed by discharge of blood, 
which has accumulated in the pharynx, down the nose. 
This is particularly seen when the animal is at work. 
Sometimes hundreds of leeches may be present at one 
time, and cause dyspnoea through obstruction of the 
pharynx. 
Treatment.—Prophylactic treatment consists in pre- 
venting the animals from drinking water from streams 
or pools infested with leeches. When this is im- 
possible, the water should be filtered through finely 
perforated metal trays, or net muzzles may be used 
while drinking. 
Curative treatment is usually successful. Strong salt 
solution on a sponge should be applied to the pharynx, 
as this dislodges the parasites. 
