ON THE EARLY STAGES OF INFLAMMATION 251 
that recovery of function had taken place to a considerable extent, but was not 
yet quite complete. 
I now felt little doubt that chloroform also possessed the power of arresting 
the pigmentary functions ; but in order to prove the fact I killed a dark frog, 
and placed one of its legs in that fluid for half a minute, and then wrapped 
both it and the other leg in damp lint. After some hours the limb which had 
not been treated with chloroform was quite pale, while the other, having lost 
the faculty of post mortem concentration, remained as dark as before. The 
appearance presented by the pigment in the two feet is shown in Plate III 
(page 68), Figs. 1 and 2. 
Mechanical violence proved similar in its effects on the pigment, which, 
in the area pinched, retained the same appearance as before, except that in 
parts where the pressure operated most severely the cells seemed sometimes 
to have suffered rupture. Fig. 2, Plate V is a camera-lucida sketch of part 
of a spot which had been compressed by means of padded forceps, with an 
adjoining uninjured portion of the web. The pigment was fully diffused before 
the experiment was performed, and remained so afterwards in the area squeezed, 
while it became concentrated elsewhere, and this was the condition of things 
when the drawing was made. The concomitant differences in tint between the 
blood in the affected and the sound parts in consequence of the accumulation 
of closely packed red discs in the former, are also strikingly shown in the sketch.! 
The galvanic shock, too, produced no effect apparent to the eye upon the 
pigment of the parts in which it caused stagnation of the blood, but experiments 
afterwards made showed me that, like ammonia, it exerted a paralysing agency 
both upon the concentrating and the diffusive powers ; and the same results 
ensued on the application of dry heat in the cases mentioned in the last section. 
From these and other similar facts it appeared that mustard, croton oil, 
and cantharides are exceptional as regards the diffusion to which they give rise, 
the usual course being that irritants, when applied so as to produce stagnation 
of the blood, suspend at the same time both the functions of the pigment-cells. 
It afterwards turned out that mustard was, in reality, no exception to 
this general rule. Subsequent experiments showed that diffusion takes place 
* Much more gentle pressure, if long continued, may give rise to similar results, as I happened to 
notice in the following manner. Being desirous of watching the process of post mortem concentration 
of the pigment, I amputated a leg of a dark frog, and, having stretched out the foot over a glass plate, 
put a small piece of thin glass upon part of one of the webs, and applied a high power of the microscope 
to it. I was disappointed to find, however, that the change I wished to observe did not take place ; 
but on looking at other parts of the web, found that immediately beyond the edge of the slip of thin 
glass the pigment was on all sides considerably concentrated, although remaining fully diffused where 
the glass covered it; an effect which I could attribute only to the gentle squeezing to which the two 
plates subjected the part of the web that lay between them. 
