REPARATORY INFLAMMATION IN ARTERIES. 83 



same time. Almost immediately after compression of the main 

 trunk the collateral branch commenced to dilate. Confining 

 the attention to what was taking place in the main trunk 

 between the branch and the point of compression, it was noticed 

 tliat for a short time the calibre of that portion of tlie artery 

 remained unaltered, and that during this time the blood within 

 it, suddenly arrested and placed out of circulation b}- the com- 

 pression, underwent no visible change in the position of its 

 elements relative to themselves or to the Avails of the vessel. 

 The only movement which could be perceived at that time was 

 that Avhich was due to the regular impulse of the heart. Soon, 

 however, this portion of the vessel began to dilate, reaching 

 finally to nearly twice its original diameter. The concurrent 

 change in the included blood-column was curious and highly 

 instructive. As the calibre of the vessel increased, the blood- 

 column did not correspondingly^ fill ont the widening space by 

 attempting to increase its diameter while shortening from 

 above downward. No doubt this shortening and spreading 

 out to some extent took place. But if it did so, it was to a 

 greatly insufficient degree, for the column began to assume a 

 curve. As the lateral resistance of the vessel-wall was remoA'ed 

 and the heart continued to impel the column from above, this 

 curve gradual)}^ shortened and bent more and more until the 

 bands became finally flattened against each other, and the 

 column was coiled in the widened lumen similarly to the suc- 

 cessive coils of a rope or of a condensing pipe. Subsequently' 

 this clot was examined under a higher i)Ower, when the serpen- 

 tine strata, of which it was composed, and the relation of their 

 elements were found to present the same characteristics, ex- 

 cept for age, as have already been stated for the lower portion 

 of the blood-clot of 48 hours. Before dismissing these obser- 

 vations it may not be amiss to remark that no acctinmlations 

 of white corpuscles sticking in masses to the walls either at 

 the side or bottom of the vessel were seen. 

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