268 " James Homer Wright. 



may attain a length greater than that of the diameter of an oil 

 immersion field. Nearly all of the cytoplasm of some cells may 

 be formed into pseudopods projecting in various directions. 



The pseudopods commonly are seen to project into more or less 

 well defined blood channels. This is especially clearly shown in 

 the spleen of the young kitten where larger and smaller pseudopods 

 are frequently seen projecting into veins through small openings 

 in the vessel wall. A whole megakaryocyte in active pseudopod 

 formation has been found in a blood vessel in the spleen. 



The amount of cytoplasm associated with a megakaryocyte 

 nucleus varies and such nuclei showing the usual signs of degen- 

 eration and senility with little or no cytoplasm about them are 

 frequent. This is due to the well known fact that the megakaryo- 

 cytes lose their cytoplasm. Thus pseudopods not connected with 

 megakaryocytes occur not rarely. 



The characteristic granules are most numerous and most closely 

 crowded together in the cytoplasm of the larger megakaryocytes, 

 of those with pseudopods, and of those in process of losing their 

 cytoplasm and in detached pseudopods. The marginal or periph- 

 eral portion of the cell body is usually free from granules, is 

 hyaline, stained blue and is sharply demarcated from the granule- 

 containing cytoplasm. The border of the cell may be smooth or 

 show rounded or irregular projections of the hyaline cytoplasm. 

 In the pseudopods the granules may be abundant throughout the 

 cytoplasm or they may occupy only the axial or mesial portions 

 leaving a sharply demarcated narrow marginal zone of hyaline 

 blue staining cytoplasm, the borders of which may be smooth or 

 show small projections of varying shape, just as does the hyaline 

 blue stained marginal portion of the blood platelets. Thus some 

 of the smaller pseudopods are identical in appearance with the 

 elongated forms of the blood platelets in everything except that 

 they are in continuity with the cytoplasm of the megakaryocyte. 



In some megakaryocytes or pseudopods one or more small 

 groups of the granules may be seen more or less definitely separated 

 by a narrow zone of hyaline cytoplasm from the rest and arranged 

 in one or more round or oval, more or less sharply outlined masses 

 which are identical in appearance and staining reaction with the 



