148 
EAllLY STAGES OF INFLAMMATION. 
the circulation of the blood in the frog’s foot, and it is proved 
experimentally that other sources of movement cannot have 
more than a very trivial influence, and that their cessation, 
supposing them to exist at all, does not give rise to arrest of 
the blood or accumulation of corpuscles in the capillaries. 
Distinct evidences of muscularity and contractility have 
been detected in the veins of the frog’s foot, but, compared 
with the arteries, the veins show very little spontaneous con- 
traction. 
Regarding the influence of changes in arterial calibre upon 
the blood in the capillaries, the author is led to conclude that 
“ the arteries regulate by their contractility the amount of 
blood transmitted in a given time through the capillaries, 
but neither full dilation, extreme constriction, nor any inter- 
mediate state of the former is capable per se of inducing ac- 
cumulation of corpuscles in the latter.” 
The influence of the nervous system upon the arteries has 
formed the subject of a special experimental inquiry, the re- 
sults of which are given in a supplement to the paper. It 
is there shown that the contractions of the arteries of the 
frog’s web are regulated by a part of the spinal cord, the ir- 
ritation of which induces complete constriction of the ves- 
sels, while its destruction is followed by permanent dilatation. 
Neither stimulation nor removal of the nervous centre for the 
arteries produces any perceptible change in the quality of 
the blood, as respects adhesiveness of its corpuscles or 
otherwise. 
Section III, “ On the effects of irritants upon the circula- 
tion in the frog’s web,” commences with an account of some 
experiments performed with tepid water applied for a brief 
period to the foot. This agent, which was selected as the 
mildest possible stimulant, produces in a very beautiful man- 
ner constriction of the arteries, followed by dilatation, with 
corresponding changes in the amount of blood transmitted 
through the capillaries, as explained at the close of Section 
II. When, however, such experiments were frequently re- 
peated upon the same animal, and especially if the tempera- 
ture of the water was more elevated, effects of a different 
kind began to show T themselves ; the corpuscles of the blood 
experiencing obstruction to their progress even while the ar- 
teries were fully dilated, and the vessels consequently in the 
state most favorable, so far as their calibre was concerned, 
for transmitting the current of blood. If the irritation was 
still continued, the minute vessels became choked with closely 
packed corpuscles. 
Subsequent experiments, with a variety of other irritating 
