248 ON THE EARLY STAGES OF INFLAMMATION 
last section, the reader will see no reason to think such an effect likely. It 
may, however, seem not improbable that the galvanic shock might, by its direct 
action upon the blood within the vessels, reduce it to the same condition as if 
removed from the body. But that this was not really the cause of the con- 
gestion, was clear from the fact that in the parts less intensely affected, where 
the corpuscles still moved slowly though possessed of considerable adhesiveness, 
the same condition continued long after all the blood which was in the vessels 
when the shock was transmitted had passed away. In this case, therefore, as 
in all the others which we have considered, the blood was affected secondarily 
to the tissues. This being established, the natural interpretation of these 
experiments appears to be, that the portion of the web affected was, as it were, 
stunned by the shock, and its functions suspended like those of the brain; the 
resolution of the inflammation, like the return of volition, depending on recovery 
of function on the part of the tissues concerned. 
From such considerations as these, it appears that all those agents which 
produce inflammatory congestion when applied to the web, though differing 
widely in their nature, agree in having a tendency to inflict lesion upon the 
tissues and impair their functional activity. 
But powerful as are the arguments thus obtained by inference, it is very 
desirable to confirm them by direct observation, and it fortunately happens 
that the cutaneous pigmentary system of the frog is a tissue which discharges 
functions very apparent to the eye, so that it is easy to trace their modifications 
under the influence of irritation. 
In the first experiment with mustard described in the last section (per- 
formed September 29, 1856), the space on which the irritant had acted presented 
a very striking difference from the rest of the web in the appearance of the pig- 
ment, which in healthy parts was in the form of small roundish black dots ; 
while in the mustard area, and accurately corresponding to the extent of stag- 
nation in the capillaries, each spot was extended to a stellate figure. 
I thus became for the first time aware that the pigment is capable of varia- 
tions, and my attention having been directed to the subject, I soon found that 
similar changes occur spontaneously, and give rise to alterations in the colour 
of the skin, which is paler in proportion as the colouring matter is more com- 
pletely collected into round spots. For some weeks I supposed myself to have 
been the first discoverer of this curious fact, till I was referred by Dr. Sharpey 
to the recent labours of the Germans on the subject. They, however, as I after- 
wards found, had taken an entirely erroneous view of the phenomenon, attributing 
the round form of the masses of pigment to contraction of the branching offsets 
of stellate cells ; whereas it turned out that the chromatophorous cells do not 
