ON THE EAREY SIAGES OF INFLAMMATION 229 
capillaries by micrometer before the application of the mustard, and again after 
it had caused stagnation in them, and found that their dimensions remained 
the same.? 
The precise limitation of the effect produced upon the blood in these two 
experiments to the area covered by the mustard, showed that it was the result 
of a direct action of the irritant either upon the blood that flowed beneath it, 
or upon the tissues of the part of the web on which it lay, the blood being in 
the latter case affected secondarily. I made several experiments to determine 
whether the adhesiveness of the corpuscles in blood out of the body was increased 
by contact with or vicinity to mustard, placing minute portions of it between 
plates of glass, and shedding a drop of blood from a frog, so that it might run 
in between the plates, and watching the result. I could, however, detect no 
evidence of such change in the corpuscles as I was seeking ; whence I inferred 
that the blood had been only affected secondarily to the tissues in the two 
mustard experiments. 
A careful study of the effects produced by the local application of chloro- 
form to the web, confirmed in every respect the conclusions previously arrived 
at. If, while the eye of the observer is over the microscope, a minute drop 
of this liquid is placed with a camel’s-hair brush upon the part in the field of 
view, it evaporates in perhaps two or three seconds ; and if the web be dry, the 
time of its disappearance can be distinctly seen. Yet though it has so short 
a time to act, it produces so powerful an effect upon the part, that the red cor- 
puscles immediately experience obstruction to their progress, and move too 
slowly in abnormal numbers through the capillaries, which perhaps become 
entirely clogged with them; the arteries meanwhile being in the state best 
adapted for easy transmission of the blood, i.e. full dilatation. In one such 
experiment I saw a few corpuscles sticking together in a capillary and moving 
with difficulty, from evident tendency to adhere to its parietes, their number 
gradually becoming augmented by the adhesion of others that followed, till 
the mass grew so large as to fill the vessel for some distance, when it finally 
stopped. In another case, the circulation being perfectly natural in the web, 
’ The increased pressure upon the blood in the capillaries, resulting from obstruction to the progress 
of the corpuscles, leads to the distension of their elastic parietes up to a certain point, but, generally 
speaking, not further. In the present case, before the application of the mustard, the web, irritated 
probably by the vapour of the chloroform, was affected with a slight congestive tendency, far short 
of that which induces stagnation, but yet sufficient to give rise to full distension of the capillaries. When 
the web has been perfectly healthy to begin with, I have seen a marked increase of calibre in the capil- 
laries on the occurrence of stagnation in them. This I noticed particularly in a case in which caustic 
ammonia was the irritant employed. I would remark, however, that the eye is apt to be much deceived 
on this point unless the micrometer is used. Those vessels which are crammed with corpuscles, being 
of dark crimson colour, look at first sight larger than others, really of the same size, which contain the 
normal ‘proportion of liquor sanguinis, and are therefore of pale tint. 
