REGULATING THE CONTRACTIONS OF THE ARTERIES 43 
the cord was divided transversely at the distance of about one-fifth of its length 
from the posterior extremity. At 4 20m p.m., just after the operation, an 
artery in the right foot measured 23°, the vessels appearing generally of pretty 
full size, and the flow of blood rapid through the web. At 4» 25™ the cord 
was again cut across a little behind the mid-scapulae, at a distance from the 
occiput of somewhat more than a quarter of the length of the cord. At 4» 33™ 
the diameter of the vessel was 14°. At 4» 4o™ the portion of cord included 
between the incisions was removed, without any interference with either the 
anterior or posterior segment. It was observed that a large branch for the 
hind legs, furnished by the middle segment, had to be divided during its 
removal, and immediately after the operation the artery measured 23°, and 
the flow of blood in the web was much more rapid than before. At 4) 45™ 
the artery had contracted to 2°, at 5 7™ it measured short of 2°, and a minute 
later was again 2°. At 5! r1™ [ introduced a fine needle into the anterior seg- 
ment of the cord with the effect of causing convulsive movements of the fore 
legs, but no change whatever in the calibre of the artery in the hind leg. 
I afterwards repeated this experiment twice, and the last time carried the needle 
on into the brain, and stirred it up thoroughly, but no effect was produced 
upon the vessel. At 5! 23™ the whole brain was removed, together with the 
anterior segment of the cord ; the artery, however, still continued to measure 2°. 
At this time the circulation, though somewhat enfeebled, was still pretty good. 
At 5 53™ a complicated operation was performed upon the left thigh, to which 
I need not allude further than to mention that it no doubt involved exposure 
of the other foot to a higher temperature than before, in consequence of the 
vicinity of my hands, and this was probably the cause of the dilatation of 
the arteries observed immediately afterwards, that which had been previously 
measured being now 22°. Five hours later the artery was again 2°, but the 
heart’s action was excessively languid. Next morning the circulation was going 
on steadily, though somewhat slowly, the heart having obviously recovered 
to some extent during the night. The arteries were larger than ever seen 
before ; the calibre of that above noted being 34°, and there were a good many 
blood-corpuscles adhering to the walls of the vessels. It is probable that the 
small posterior segment of the cord had become impaired in its powers, but 
that it was still acting to some extent was evident from the circumstance that 
after its removal at roh 56™ a.m., the vessel was found increased to 4°, and 
in consequence of the arterial dilatation, the stagnation of the red corpuscles, 
which existed in several parts of the webs, was almost entirely dispelled, 
although the action of the heart did not appear to have been changed. During 
the next half-hour the artery was measured four times, and was in every in- 
