J 28 HOWELL. [Vol. IV. 



through it, and hence the most natural explanation is that it 

 is a material secreted by the cell which is finally dissolved in 

 the plasma, and is used, possibly, for the nutriment of the 

 blood-forming cells ; though this, of course, is mere speculation. 

 In sections nothing remains of the material except the reticu- 

 lum, and this does not stain with any of the reagents used, — 

 alum carmine, hasmatoxylin, eosin, saffranin, Ehrlich-Biondi's 

 stain, indigo carmine (Shakspeare-Norris stain), ^ or at least 

 stains much more feebly than the protoplasmic cell substance. 



Summary. 



The contents of the paper may be summed up briefly as 

 follows : 



1. Giant cells fall into two classes: a. Polykaryocytes, or 

 multinucleated giant cells found in developing bone, in patho- 

 logical formations, or porous bodies kept in lymph cavities, 

 etc. ; b. Megakaryocytes, or large nucleated giant cells found 

 in the red marrow of the adult and in the blood-forming organs, 

 liver, spleen, etc., of the embryo. 



2. The polykaryocytes have no special function, are not 

 related to the megakaryocytes, and are formed by the fusion 

 of smaller cells in consequence of too rapid growth. 



3. The megakaryocytes form a peculiar class of cells. They 

 arise from the growth of small lymphoid cells, and afterwards 

 reproduce by direct division. During their life they form a 

 secreted material which can be seen for a time by the micro- 

 scope, but finally dissolves in the plasma. 



They seem to take no direct part in the production of nucle- 

 ated red corpuscles or erythroblasts. After a certain period 

 the nucleus alters in such a way that it stains diffusely and 

 then fragments. This seems to be a degenerative change, and 

 probably ends in the total disintegration and dissolution of 

 the cell. 



