ON: THE DARL Y STAGES OF INFLAMMATION 233 
in consequence of nervous irritation ; the general impression conveyed by the 
experiments with warm water above related being that arterial contraction 
was most apt to show itself when the degree of irritation was least, while dilata- 
tion was most marked when the stimulus was strongest. I have lately seen 
a Striking illustration of this principle in a very simple experiment, which I was 
induced to make in consequence of reading a paper recently published by a 
French author, M. J. Marey.’ If a blunt-pointed instrument, such as the end 
of a pair of dissecting forceps, is drawn with gentle pressure along the back of 
the hand while it is in a state of moderate redness, the blood being driven out 
of the vessels, a pale streak results, which immediately disappears, in conse- 
quence of the return of the blood into the part. In a few seconds, however, 
a pale stripe, towards a quarter of an inch in breadth, becomes developed at 
each side of the line along which the instrument passed, that line having now 
assumed a red colour, if the pressure employed was at all forcible. This is 
M. Marey’s experiment ; and there can be no doubt that his interpretation 
of the secondary paleness is correct, viz. that it depends on reflex arterial con- 
traction. The red line, when it occurs, is evidently due to the direct action 
of the pressure upon the tissues, being, as M. Marey correctly states, exactly 
of the same breadth as the instrument used. But I find that if the pressure be 
made with considerably greater force, so as to be positively painful, while the 
first white streak appears as before in consequence of the blood being dispelled 
from the vessels, the secondary paleness does not occur, but, on the contrary, 
a patch of the adjacent skin, extending for perhaps half an inch on each side, 
assumes abnormal redness, which lasts for a longer time than the paleness to 
which the other experiment gives rise. Here, the irritation being severe, the 
blood vessels are thrown through the medium of the nervous system into a state 
of muscular relaxation, instead of the contraction which is induced by a more 
gentle application of the same stimulus. 
To return to the consideration of inflammatory congestion. Further light 
was thrown upon the condition of the blood in the vessels of an irritated part 
by a series of observations made when the circulation had been arrested by 
amputation of the limb, or by a ligature round the thigh. This field of inquiry 
was unexpectedly opened during the course of an experiment made with a view 
to ascertaining the effects produced by an irritant upon the pigmentary system 
independently of the circulation, as will be described in the next section. On 
the 13th of October, 1856, a frog having been killed by destruction of the brain, 
1 Recherches Hydvauliques sur la Circulation du Sang, par M. J. Marey. The separate copy of this 
paper, sent me by the author, does not contain any mention of the Journal in which it was published, 
so that I am unable to give proper reference to it. 
