442 Dr. Philip’s additional experiments on the 
removed, the web of one of the hind legs brought before the 
microscope, and the circulation in it, which was rapid, observed. 
A strong infusion of tobacco was then applied to the brain, 
with the effect of at first rendering the circulation more rapid. 
In about half a minute it became more languid, and soon 
stopped altogether. On the infusion of tobacco being washed 
off’, the circulation returned and regained considerable vigour. 
The tobacco was several times applied to the brain and 
washed off, with the same effects. I may observe, that when 
the circulation in the web had almost ceased after the tobacco 
had been washed off, its velocity was immediately increased 
on applying spirit of wine to the brain. 
Exp. 16. Analogous to what I had occasion to observe 
respecting the heart, I could never, either by chemical or me- 
chanical agents, excite any irregular action in the blood ves- 
sels. Their action "was only rendered more or less powerful. 
The irregular appearances in the circulation in the web 
of a frog’s foot, mentioned by Dr. Thompson, Professor of 
Military Surgery in the University of Edinburgh, in his Lec- 
tures on Inflammation lately published, and which he ascribes 
to inflammation, may be observed in any case, if the vessels 
be at all compressed in applying the foot to the microscope ; 
and although they are not compressed, these appearances very 
generally occur when the circulation begins to fail. The 
blood will then stop and go on at intervals, and move back- 
wards and forwards in the same vessel. I have often watched 
the capillaries from the commencement of inflammation to its 
greatest height, when the part is about wholly to lose its 
vital pow'er, in the mesentery of a rabbit, the w^eb of a frog’s 
