ON THE EARLY STAGES OF INFLAMMATION 255 
three irritants assumes a high interest, as visible evidence of diminished functional 
activity accompanying, if not preceding, the earliest approaches to inflammatory 
congestion in parts which have been subjected to their influence. 
With the view of ascertaining the nature of the effect produced on the 
pigment-cells by the mildest action of chloroform which is capable of causing 
inflammatory disorder, I ascertained, by repeated experiments, the shortest 
time in which the vapour of that liquid gave rise to unequivocal signs of a con- 
gestive tendency in the web of the living frog; and having found this to be 
about half a minute, suspended for that period one of the legs of a recently 
killed dark frog in a vessel, the bottom of which was covered with chloroform, 
having previously examined the webs microscopically, and found that full diffu- 
sion of pigment existed throughout them. The result was that the limb exposed 
to the chloroform vapour remained dark, while the other became gradually pale. 
On re-examination of the former after some hours, each web presented stripes 
of full diffusion of pigment alternating with others in a medium condition ; their 
direction being at right angles to the margin of the web. The longitudinal 
folds in which the webs had happened to be, had prevented the chloroform 
vapour from gaining equally free access to all parts ; yet the chromatophorous 
cells in the stripes that had been thus partially protected from its influence had 
been incapable of complete concentration, showing that even the exceedingly 
slight degree of action which the chloroform could have exerted upon these 
places sufficed to diminish, though not to destroy, the functional activity of 
the pigmentary tissue. 
In one of the experiments performed in order to determine the effect of 
mechanical violence, as before alluded to, the pigment remained unchanged 
for days in the area which had been pinched, while varying in other parts of 
the web ; yet, though great excess of red corpuscles existed in the vessels of the 
affected spot, they never ceased to move; showing that the functions of the 
pigment-cells might be completely suspended by a degree of irritation short of 
that which occasions actual stagnation of the blood. 
The same thing was afterwards? seen in a case in which a small drop of 
wood-vinegar was placed upon one of the webs of a frog which had been deprived 
of the power of voluntarily moving the limbs by passing a knife between the 
occiput and the atlas, so as to sever the brain from the cord. The fluid being 
thus allowed to lie quite undisturbed, did not spread at all upon the web, which 
was dry before it was applied. It produced its effects very slowly, so that, 
after the lapse of three and a half hours, the blood in the area covered by it, 
while everywhere presenting inflammatory appearances, was still only partially 
* This experiment was performed subsequently to the reading of the paper. 
