158 TWO-TOED SLOTH. 
cient for the foundation of any theoretical expla- 
nation of the slow movement of the muscles. 
The British Museum afforded an opportunity of 
investigating this particular in other slow-moving 
Quadrupeds, and Mr. Carlisle^ at my request, 
examined the arteries of the Bradypus tridactylus, 
of all Quadrupeds yet known the slowest in its 
movements; when the same remarkable distribu- 
tion of vessels presented itself, both in the upper 
and lower limbs ; and the small divisions of the 
artery, forming the surrounding cylinder, were 
still more numerous than in the Slow Lemur, viz. 
not less than 60 or 65, and in the lower limbs^ at 
least, as many : these small cylinders were also 
connected by several lateral or anastomosing 
branches. We then opened a specimen of the 
Bradypus didactylus, an animal far less slow in 
its motions than the tridactylus. In this species a 
distribution indistinctly approaching to that above 
described was discovered, but with much fewer di- 
visions, and more approaching to the usual distribu- 
tion in other Quadrupeds. Lastly, A Lemur Loris, 
or Slender-limbed Lemur, was examined ; when it 
appeared that the trunk of the artery, both in the 
upper and lower limbs, was surrounded by only 
four or five smaller cylinders, instead of the nu- 
merous ones so remarkable in the Slow Lemur, kc. 
