2 6/^ Sir Everard Home on the structure of the organs , 
mm. The organs themselves. 
nn. The mucous glands. 
Plate XIII. 
The respiratory organs in the aphrodita aculeata and leech. 
Fig. 1 . Back view of the aphrodita aculeata. 
Fig. s. The respiratory organs laid bare by removing the 
skin and muscles of the back. 
aa. The cells projecting into the cavity under the muscles 
of the back. 
hh. The external openings leading into the cavity. 
c. The gizzard exposed, the thin cartilaginous covering 
seen on the opposite side having been removed. 
d. The intestine. 
ee. The lateral tubes going off on each side. 
ff. The caeca, which project into the cells. 
Fig. 3. The hirudo medicinalis laid open from behind, the 
stomach removed, exposing the respiratory organs, consist- 
ing of thirty-two transparent cells, in each of which the ex- 
ternal orifice is seen through the coats. 
The spinal marrow with its ganglia and nerves distinctly 
seen. 
aa. The respiratory cells. 
bb. A large blood vessel on each side. 
cc. Mucous glands. 
dd. Glandular structures communicating with the testicles. 
ee. The testicles. 
f. The penis. 
g. The uterus. 
