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actively or passively and the nucleus is carried along with it. On 

 watching the process closely we are under the impression that it is 

 rather a passive act than a manifestation of vital activity. The 



Fig. 3. Spleen of cat 2 weeks. Zenker Iron-hematoxylin-eosin. + ^^^ X 

 natural size. a. megakaryocyte with a long protoplasm-filament in the lumen of 

 the vein, no longer stainable at the extremity. Nucleus pyknotic; still lying in the 

 spleen-pulpa. h like a, but the shrivelled nucleus lying just in the lumen of the 

 vessel, c. degenerating megakaryocyte lying entirely in the vein, d megakaryocyte 

 with easily stainable cytoplasm, without filaments, but with markedly pyknotic nucleus. 

 e. vessel-wall. 



filaments of the protoplasm (they can no longer be called pseudopods) 

 extend invariably < in the same direction in the same bloodvessel 

 (Fig. 3 a and b). It would seem then that the protoplasm is carried 

 along by the blood-stream, when once it has entered into the 

 lumen of the vessel. Now it is still a subject of dispute whether 

 the vessel-wall in the spleen is closed or whether there are openings 

 in it. When assuming the latter, the limp, inert, degenerating giant- 

 cells, lying close to the vessel-wall, are supposed to be pressed 

 through the openings in the vessel-wall, when the spleen contracts. 

 This squares, with the appearances presented by the megakaryocytes 

 in these preparations. 



For, if it were an active diapedesis we should see a pseudopod, 

 after it had once protruded through the bloodvessel, lodged against 

 the opposite side of that vessel ; now this we do not see anywhere. 

 Contrariwise we see that a protoplasm-process is gradually prolonged 

 in the lumen of the vessel and dissolves. If sometimes a whole cell 

 is seen in the lumen of the vessel, all sorts of irregular protoplasmic 

 strands are seen to form (Fig. 1 a and b), while the detached 



