in the Arteries of slow-moving Animals. 1 g 
quickly subdivided than the arteries of muscles generally. The 
alteration which the blood undergoes during the supply of this 
muscle only, is worthy of remark, viz. that the coronary veins 
return venous blood apparently as much changed from the 
arterial state, as if it had passed through the remotest organs of 
the body. 
Any impediment to the accustomed course of the blood 
flowing through muscles, induces a corresponding diminution 
in their powers of action. When the principal arterial trunk 
which supplies the muscles of the leg is obliterated by ligature, 
for the cure of an aneurism, the leg remains afterwards much 
weakened in its muscular strength, until the circuitous vessels 
have again restored a vigorous supply of blood. 
Animals with prehensile tails, such as certain monkeys and 
opossums, have the muscles of their tails supplied by one cy- 
lindrical artery; and the length of time they can suspend 
themselves by their tails is remarkable, notwithstanding the 
assistance derived from the repetition of coils around the bough 
of a tree, and occasionally from an elastic bend in the extreme 
joints of some prehensile tails. 
The swimming-bladders of some fishes afford another ex- 
ample of cylindrical arteries supplying the muscular parts of 
them. (See Plate I. Fig. 1.) That these parts are truly muscular, 
I have ascertained by their excitation with the Galvanic metals. 
The swimming-bladders appear destined to assist the fish in 
rising or descending in the water, as well as to keep the back 
upwards when at rest ; so that their muscular actions are pro- 
bably of slow performance, and require to be of long continuance. 
The intestinum ileum of the Cavia Aguti has a similar dispo- 
sition of blood-vessels ; from which I was led to consider the 
D 2 
