C 17 3 
II. Continuation of an Account of a peculiar Arrangement in the 
Arteries distributed on the Muscles of slow-moving Animals , 
&c. In a Letter from Mr. Anthony Carlisle to John Symmons, 
Esq. F. R. S. 
Head December 8, 1803. 
DEAR SIR, 
Y ou did me the honour of presenting to the Royal Society, An 
Account of a Peculiarity in the Distribution of the Arteries sent 
to the Limbs of slow-moving Animals.* According to my in- 
tention expressed in that letter, I have, since that time, endea- 
voured to collect farther illustrations of the connection between 
the disposition of the blood-vessels and the actions of muscles. 
Neither the tribe of ruminating, nor the carnivorous animals, 
have afforded the evidence which I had expected, from the in- 
vestigation of their masseter, pterygoid, and temporal muscles ; 
since these are all supplied by the ordinary arborescent arteries. 
The rete mirabile, in such animals, seems to be a contrivance to 
restrain that velocity of the blood which their habits and figures 
would otherwise produce, in its passage to the brain. The cir- 
cuitous course of all the arteries which supply the human brain, 
and their confinement in bony passages, is obviously for a 
similar purpose. Having sought for examples in other directions, 
the following results have occurred. 
In the human body, two small arteries arise from the upper 
* See Phil. Trans, for i8co, p. 98. 
D 
MDCCCIV. 
