260 ON THE EARLY STAGES OF INFLAMMATION 
alluded to,! that mustard produces a similar result on the cutaneous sensory 
nerves, and hence it seems probable that the same is true of the whole class of 
irritants. Again, the diffusion induced by mustard, croton oil, and cantharides 
indicates, according to what we have seen to be its most probable explanation, 
that the nerves of the pigment-cells suffer impairment of functional activity 
under the action of these three substances. On the other hand, the fact that 
diffusion is arrested equally with concentration by most irritants, appears to 
prove that the chromatophorous cells are themselves also affected with loss 
of power ; for, as has been before alluded to, the withdrawal of nervous influence 
from them in a healthy state of the tissues invariably gives rise to diffusion, 
and the same result would necessarily follow the action of an irritant which 
merely paralysed the nerves. I have also observed, on two occasions, after the 
energetic operation of an irritant upon a part of a web containing a large artery,” 
that drawing the point of a needle firmly across the vessel failed to induce the 
slightest contraction in it, even at the very point crossed by the needle ; proving 
that the muscular fibre-cells had lost their irritability. At the same time it is 
by no means improbable that the nerves of the arteries may suffer before their 
muscular constituents, just as in the intestines, after death, the functions of 
the intrinsic nervous apparatus are lost some time before muscular contractility 
ceases.” 
The question whether the suspension of function induced by irritants is 
confined to the nerves or affects the tissues generally, being one of great interest, 
I was anxious to obtain clear evidence regarding it; and it occurred to me 
that valuable information would probably be derived from observing the effects 
of such agents upon the action of the cilia, which, though not present in the 
web of the frog, exist in abundance upon the mucous surfaces of the mouth and 
oesophagus of that animal. Dr. Sharpey, in his celebrated article ‘ Cilia’ in 
the Cyclopaedia of Anatomy and Physiology, mentions experiments made by 
Purkinje and Valentin, and also by himself, with a great variety of substances, 
including among the rest some irritants, which, when applied with sufficient 
energy, arrested completely, by their chemical action as it was supposed, the 
* See p. 2394. 
* The main arteries lying between the layers of skin of which the web consists, are not so speedily 
acted upon by irritants as the capillaries of the dermis. This is most marked in large frogs with thick 
webs. In one such specimen, a drop of chloroform caused first stagnation and then discoloration from 
chemical action on the blood in the capillaries of the dorsal layer of the web to which it was applied, 
while a main artery lying beneath still contained blood of natural appearance, and showed evidence of 
Janguid contractility, while in the capillaries of the plantar layer of the web, the circulation was still 
going on in a pretty healthy state. This frog, however, seemed endowed with unusual powers of vitality 
in the tissues. This observation, as well as that in the text to which this note refers, was made subse- 
quently to the reading of the paper. 
* See the paper ‘ On the Functions of the Visceral Nerves ’, before referred to (p. 87 of this volume). 
