GIANT-CELLS OF BONE-MARROW 121 



granules did not stain as intensely as did the mitochondria of 

 certain other tissues similarly treated, e.g., those of the cells of 

 the onion membrane; 2) the granules seemed too minute for 

 mitochondria of such presumably highly differentiated cells, 

 and the possibility presented itself that they might be the meta- 

 chromatic granules revealed with Wright's technic; 3) it seemed 

 probable that these cells should contain some bacillary and filar 

 mitochondria. 



Accordingly, experiments with various fixing and staining 

 technics were next undertaken. The only technic which gave 

 acceptable results was fixation in a 2 per cent osmic-acid solution 

 applied for four weeks. This method reveals abundant granular 

 and annular (vesicular) mitochondria in the cytoplasm of the 

 giant-cells (figs. 5 to 11). An occasional small bacillary mito- 

 chondrion also appears, but no filar mitochondria are present in 

 my preparations. It seems, therefore, that the granules revealed 

 by the j anus-green solution in the fresh material are actually 

 the mitochondria. The slightly larger size of the mitochondria 

 in the fixed preparations may be the result of a slight swelling 

 action of the osmic acid. Moreover, the metachromatic granules 

 revealed by Wright's technic are more minute, irregular, fre- 

 quently clumped, and to some extent of a dust-like nature. The 

 relation of the mitochondria to the metachromatic granules has 

 not been determined. 



Cowdry's ('14) illustrations of living blood platelets stained 

 with janus green, showing granular mitochondria, support my 

 conclusion that the granules of the giant-cells revealed by the 

 Kopsch technic are mitochondria. The platelets illustrated by 

 Cowdry showing bacillary mitochondria may be of the sort 

 derived from hemoblasts, or even from lymphocytes. In the 

 red bone-marrow of the frog it has been shown that all varieties 

 of leucocytes may produce platelet-like bodies, and it seems 

 altogether probable that in mammals also lymphocytes may to 

 a variable extent contribute to the sum of blood platelets formed 

 predominantly by hemogenic giant-cells ('19 b). 



In my best set of preparations mitochondria are revealed 

 only in the hemoblasts and the hemogenic giant-cells. No 



