ON THE EARLY STAGES OF INFLAMMATION 249 
alter in form, but that the colourless fluid and dark molecules which constitute 
their contents are capable of remarkable variations in relative distribution, the 
molecules being sometimes all congregated in the central parts of the cells, the 
offsets containing merely invisible fluid, while at other times the colouring 
particles are diffused throughout their complicated and delicate branches ; and 
between these extremes any intermediate condition may be assumed. It 
further appeared that concentration of pigment takes place in obedience to 
nervous influence, while diffusion, though also an active vital process, tends 
to occur when the pigment-cells are liberated from the action of the nerves. 
But for further particulars on this subject, I beg to refer the reader to a 
previous paper in this volume." 
The contrast between the pigment in the area on which the mustard had 
acted and that of surrounding parts in the case last alluded to, at once struck 
me as probably the result of a direct action exercised upon the tissues by the 
irritant. It seemed possible, however, that it might be a secondary effect of 
the state of the blood in the congested vessels ; and in order to ascertain which 
was the truth, I performed, on the 14th of October the following experiment :— 
Having cut out a piece of the web of a healthy frog, I placed a small portion 
of mustard upon its centre when all the blood had escaped fromit. After a while 
the spots of pigment seen through the thin margin of the mustard, presented 
a stellate form, while in the rest of the piece they were still of a rounded figure. 
Hence it was clear that the change in the disposition of the pigment was the 
result of the direct action of the mustard upon the tissues of the web. 
A new field of investigation was thus opened before me, promising to throw 
great light upon the nature of inflammation. 
To explain the effects of irritants upon the pigmentary tissue proved, 
however, to be a matter of considerable difficulty. Tincture of cantharides and 
croton oil, which happened to be among the first substances which I employed 
with reference to this subject, resembled mustard in causing diffusion of the 
pigment. Taking, in the first instance, the same view of this change as the 
German authorities, I attributed it to the relaxation of contractile cells, and 
regarded its occurrence, in consequence of irritation, as an indication of loss 
of power in the tissues, a view which was in harmony with the nature of the 
derangement of the blood in a congested part. Croton oil, curiously enough, 
acted very slowly on the web, not producing any change on either pigment or 
blood for an hour or more : also its effects appeared inconsistent with my theory ; 
for while it ultimately gave rise to diffusion of the pigment to even a greater 
extent than I had seen occur with mustard, yet it induced only comparatively 
HSEE Pps 4d St Seq. 
