38 ON THE PARTS OF THE NERVOUS SYSTEM 
was greatly enfeebled by this operation; and at 64 45™ they had [attained 
nearly the full diameters that the hot water had before induced, while the 
circulation had somewhat recovered. Next morning the arteries of the two feet, 
the dimensions of which were before given, measured 4° and 3° respectively, 
and they continued without the slightest variation until 5! 25™ p.m.; the 
circulation meanwhile had continued to improve, and was healthy, though 
still languid. I then removed the remainder of the cord and the entire brain 
without producing any effect whatever on the size of the arteries, and they 
still measured precisely the same at Io! 45™ p.m. The following morning the 
frog was dead, and the tissues of the web had become opaque by the imbibition 
of water. 
In this case the arteries recovered their contractile power after the removal 
of the greater part of the posterior half of the cord, together with the chief 
roots of the nerves for the hind legs ; but when the part which furnishes branches 
to the posterior extremities had been completely removed, the arteries became 
permanently dilated ; and, though the circulation was then feeble, soon attained 
the full calibre which hot water had induced at a time when the heart was in 
powerful action. 
The perfect constancy with which the vessels observed maintained these 
dimensions for more than thirty hours after the operation, implied that they 
were not then at all acted on by the nervous system; and hence I was led 
at first to infer that there existed no other ganglionic apparatus for the arteries 
of the feet than that contained in the cerebro-spinal axis. 
I have since witnessed in other frogs the permanence of the dilatation 
of the arteries after removal of the brain and cord. The following case, how- 
ever, appeared at first inconsistent with these observations. On the 23rd of 
October the brain and cord of a large frog were completely removed, and an 
operation was performed upon the right thigh, which, as it turned out, tended 
to interfere with the freedom of the circulation in the webs; so that after 
twelve hours, the blood, though not presenting the appearances of inflammation, 
was almost motionless in that foot. At the same time, two arteries in one of 
the webs, which had till then remained perfectly constant in calibre, as deter- 
mined by micrometer, began to exhibit variations, and during the next twenty- 
four hours continued to change their diameter occasionally. There were, how- 
ever, certain peculiarities about these changes such as I had never before seen. 
Generally speaking, all the arteries of a web are found in the same degree of 
contraction at any one time; but here, one of the vessels under observation 
* This was the view expressed in the original manuscript, but it has been since modified by further 
experiments mentioned in the text, made, as their dates imply, subsequently to the reading of the paper. 
