32 
CLASS ANNELIDA. 
The ganglia of the nervous cord are much more separated 
than in the lumbrici. 
The leeches are hermaphrodites : a large penis projects 
from under the anterior third of the body, and the vulva is a 
little farther back. Many of them collect their eggs into 
cocoons, enveloped in a fibrous excretion. 
They have been subdivided according to characters chiefly 
derived from the parts of the mouth. 
SANGUisflGAjjSfaw., Jatrobdella, These are the 
leeches properly so called ; the anterior sucker has its upper 
lip divided into several segments ; its aperture is transverse, 
and it contains three jaws, armed, each on its edge, with two 
ranges of very fine teeth, which enables them to penetrate 
through the skin without making any dangerous wound there. 
Ten small points have been observed upon them, which are 
taken for eyes. 
We are all acquainted with the common or medicinal leech, 
Hirudo medicinalis , L., so useful an instrument in local 
bleedings. It is usually blackish, striped with yellowish 
above ; yellowish, spotted w r ith black underneath. It is found 
in all dormant waters. 
ELemopsis, Sav., differ from the last only because their jaws 
have but a few and obtuse teeth. M. de Blainville calls them 
Hypoldella , the Horse-leech ; Hirudo sanguisuga , L. ; 
Hcemop. sanguisorba , Sav., Moq. Tand. pi. iv. f. 1.; Car.pl. 
xl. f. 7. ; much larger, and altogether of a greenish black. It 
has been reported to be sometimes dangerous, from the wounds 
wdiich it inflicts. 
The difference of opinions as to the pow r er of the horse- 
leech to draw blood is very singular. Linnaeus says that 
nine of them can kill a horse. MM. Huzard and Pelletier, 
on the contrary, in a memoir lately presented to the Institute, 
and inserted in the Journal de Pharmacie, March, 1825, as- 
sure us that it never attacks a vertebrated animal. M. de 
