304 THE AMERICAN MONTHLY [Oct., 



last ten I observed the mesenteries only. I tried to ob- 

 serve as carefully and as long at a time as I could, and I 

 would say here that it is only by watching this process 

 of inflammation from the time it commences until we 

 can no longer follow it with our microscope, without 

 once taking our eyes from it, can we hope to see and un- 

 derstand all of its phenomena ; but in my own case I 

 found it intensely tiresome to observe longer than eight 

 consecutive hours at a time so that I probably missed 

 much that I might otherwise have seen had I had greater 

 endurance and patience. 



EXAMINATION OF FOOT-WEBS. 



I examined the foot web of a frog with a medium 

 power say a § in. objective. The first thing noticed is the 

 great number of vessels and capillaries, filled with a 

 swiftly moving current of blood ; so swiftly, indeed does 

 it move, that the constituents of the blood cannot be dis- 

 tinguished, and we see it only as a never ending motion 

 without known composition. 



At various situations in the field beautifully branched 

 pigment cells are seen and on carefully focussing we can 

 distinguish the cells of the surface epithelium, each cell 

 containing a barely distinguishable nucleus. This is the 

 appearance of the web before it is acted upon by an irri- 

 tant, and such will be the appearance for hours, if the 

 part is kept moistened and not irritated. 



But on touching tlie web lightly with nitrate of silver, 

 or even scratching it with a needle, we get an entirely dif- 

 ferent appearance, and the process of imflammation be- 

 gins. At once there is a dilatation of the arteries, this 

 dilatation extending gradually to the veins and capilla- 

 ries. As far as I could determine this dilatation was 

 not preceded by any contraction, and aft'ected the arte- 

 ries mostly, and the capillaries but slightly, although the 

 ratio may have been alike. This dilatation seemed to in- 



