274 ON THE EARLY STAGES OF INFLAMMATION 
PLATE V 
represents the effects produced by irritants upon the pigmentary tissue and the blood-vessels , 
of the frog’s foot. 
Fig. 1 shows the results of the application of mustard to the web. The pigment was at first in the 
stellate condition as on the left-hand side of the sketch, and it remained permanently in that 
state in the part on which the mustard lay, while at the same time intense inflammatory con- 
gestion was produced there, indicated by the deep red colour of the vessels. Just beyond the 
edge of the mustard the irritating vapour of the volatile oil gave rise to full diffusion of the pig- 
ment (an effect peculiar to mustard and a few other irritants when acting mildly), but without 
material inflammatory disorder of the blood ; as seen in the stripe down the middle of the draw- 
ing. During the progress of the case the animal changed to a pale colour in the body generally, 
assuming the dotted aspect depicted on the right-hand side of the sketch in all parts which had 
not been acted on by the mustard, and thus deprived for the time being of the power of concen- 
tration. It will be observed that the blood-vessels of the healthy part are not materially smaller 
than those of the congested region ; the deep colour of the latter being due to their containing 
closely packed red corpuscles, while the former are pale in consequence of the blood within them 
having the normal proportion of colourless liquor sanguinis. 
Fig. 2 illustrates the effects of mechanical violence. The lower half of the sketch represents parts of an 
area in one of the webs of a dark frog, which was pinched with a pair of padded forceps so as to 
give rise to inflammatory congestion. The animal afterwards grew much paler, so that in healthy 
parts the pigment assumed the angular or slightly stellate appearance shown in the upper part 
of the drawing. But on the particular spot on which the mechanical violence had operated, the 
chromatophorous cells being incapable of discharging their usual functions, the pigment remained 
in the fully diffused state in which it was at the commencement of the experiment. 
