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SUPPLEMENT 
with the stomach is made by an extremely narrow orifice; it 
has a similar opening into the rectum, which latter proceeds 
directly to the anus, which is very small, and pierced in the 
last ring of the body. 
No author has spoken of a liver in the leech ; yet M. de 
Blainville regards as such the cellular system, already men- 
tioned, of a deep brown, which clothes externally, in the form 
of a membrane, the greatest part of the intestine and stomach. 
The respiratory apparatus, according to the generality of 
observers, does not exist in a specific manner in the leeches. 
The circulatory system is considerable and very complicated 
in these animals : it is composed as usual of a venous and arte- 
rial system, but there is no heart, properly so called. 
The venous system is formed of two very long vessels, with 
their distinct parietes, situated underneath each side of the 
body, between the intestinal canal and the longitudinal stra- 
tum of muscles of the external envelope. These vessels, 
which are evidently larger in the middle than at the extremi- 
ties, receive in their passage a great number of transverse 
branches, some of which return from the tissue itself of the 
animal, and others come from the vessel on the opposite side, 
from which it follows that these two large veins and their 
ramifications form a net-work with broad meshes on the back 
of the leech. 
Towards the anterior extremity these two veins are con- 
tinued in branches which curve upwards, and unite in the 
middle and dorsal line to a smaller vessel, but with parietes a 
little thicker, placed in a longitudinal furrow, hollowed in all 
the length of the intestine. This is the aorta, from which 
spring, at a right angle from the two sides, the vessels des- 
tined by their ramifications to carry the blood into all the 
parts of the body of the animal, but especially to the parietes 
of the intestinal canal. 
The reproductive apparatus, or system of generation, is 
