28 THE TONER LECTURES. 



position now for the first time appeared to have undergone 

 some change. Tlieir index of refraction had slightly lessened, 

 and their substances had begun to imbibe the carmine — previ- 

 ously they had remained entirely unstained. Through growth 

 of the cellular covering of the intima, the walls of the plastic 

 cup or clot now generally extended some distance above the 

 position of the blood or fibrinous clot, sometimes as far as the 

 first collateral branch. The cellular infiltration of some of the 

 tissues in the neighborhood of the ligature was very decided. 

 The adventitia and the adjacent connective tissue, as also to a 

 slight extent the media, here presented points approaching to 

 a purulent infiltration — an obvious preparation for the separa- 

 tion of the ligature. This infiltration extended some distance 

 above and below the ligature ; but in proportion as the dis- 

 tance from the latter increased, the infiltration became more 

 and more limited to the internal portion of the adventitia and 

 to the external layer of the media. No tendency of the capil- 

 laries or other vessels of the vaso vasorum, which were as yet 

 entirely confined to the outer coat and the external layers of 

 the media, to send projecting loops toward the lumen of the 

 artery could be observed. A transverse section, extending 

 through the vessel at such a IcA'el that its plane passed irame- 

 diaiely below the bottom of the blood-clot, showed a consider- 

 able cellular increase in those inner layers of the media in appo- 

 sition with the elastic layer of the intima. This cell increase 

 could still be discovered even in cross-sections at the level of 

 the apex of the blood-clot, but there it was not well marked. 



Fig. 3. Preparation forty-eight hours old. Transverse sec- 

 tion extending through plastic clot. High power, c. Cellular 

 tissue, showing cell increase, a. Adventitia, also showing 

 increase of cell elements, but not so markedly, m. Media, 

 in its inner hyer showing considerable cell proliferation, e. 

 Folds of elastic layer of intima still very distinct and hiuhly 

 refrnctive, yet showing a tinge of carmine which cannot be so 



