21 
in the Arteries of slow-moving Animals. 
I have considered the accompanying figures of the arteries on 
the swimming-bladder of the tench, as a striking additional 
illustration of the subject, though they have been often noticed 
before, and occasionally ill represented. The intestinum ileum 
of the aguti is also figured, to show the same kind of distribu- 
tion. The vessels in both having been injected, for the purpose 
of a clearer representation. 
References to the Figures, Plate I. 
Fig. 1 represents a side view of the double swimming-bladder 
of the tench. (Cyprinus Tinea.) The arteries on one side of the 
hinder bladder being drawn as they appear when injected. The 
upper portion of the bladder is devoid of those kind of vessels, 
and does not appear to be muscular. In the hinder portion of 
the swimming-bladder of the barbel, ( Cyprinus Barbus ,) these 
parallel cylinders wind spirally round the bladder, instead of 
proceeding straight forward along the sides. 
а , The ductus pneumaticus entering the hinder portion of the 
vesica aerea. 
б, The trunk of the artery from whence the bundles of cy- 
linders are distributed. 
c, The upper portion of the vesica aerea, which is covered by 
a thick, white, opaque, tender membrane. 
