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corpuscles of the blood experiencing obstruction to their progress 

 even while the arteries were fully dilated, and the vessels consequently 

 in the state most favourable, so far as their calibre was concerned, 

 for transmitting the current of blood. If the irritation was still 

 continued, the minute vessels became choked with closely packed 

 corpuscles. 



Subsequent experiments with a variety of other irritating agents 

 showed that the corpuscles, both red and white, were obstructed in 

 their progress through the irritated part, in consequence of their 

 tending to adhere in an abnormal degree to one another and to 

 the walls of the vessels. The effects upon the blood were always 

 similar, although the means employed to produce irritation were 

 exceedingly various, such as solutions of salts, mustard, essential 

 oils, chloroform, heat, galvanic shock, mechanical violence, &c. 



The irritant was generally so applied as to act only upon a small 

 area of one of the webs, and it was found that the abnormal ad- 

 hesiveness of the blood-corpuscles was in the first instance always 

 precisely limited to the spot which had been thus acted on, though 

 it frequently extended afterwards more or less to surrounding parts. 

 At the same time the vessels of the irritated spot did not differ 

 materially in calibre from those in its vicinity which participated in 

 the arterial dilatation induced by the stimulus. The exact corre- 

 spondence between the extent of the irritant application, and that of 

 the effect upon the blood, showed that the latter must be due to 

 direct action either upon the blood itself or the tissues of the web. 

 That it was not the result of direct action upon the blood was 

 evident from the two following considerations. In the first place, 

 most of the agents employed to cause irritation, when applied to 

 freshly drawn blood, either had no effect upon the corpuscles, or 

 destroyed instead of increasing their adhesiveness. Secondly, if 

 employed so as to act mildly on the web, they induced an abnormal 

 condition of the blood, short of actual stagnation though very ap- 

 parent, namely, slow movement of numerous and adhesive corpus- 

 cles ; and this state of things might last, although the time of 

 operation of the irritant was often limited to a few seconds, or 

 even a still briefer period. Long after all the blood which could 

 possibly have been directly acted on had left the vessels of the 

 part, successive fresh portions continued to experience precisely 



