No. 3] BLOOD-PLATES OF THE HUMAN BLOOD. 649 



zone into an inner and outer layer, the inner one being much 

 lighter in color. The outer layer sends out a number of cyto- 

 plasmic projections and filaments, which frequently are longer 

 than the diameter of the main body of the blood-plate. 



Recapitulating, we find that the blood-plate contains the 

 following zones or spheres, more or less concentrically arranged. 

 Counting the innermost first we have : 



1. A highly refractive, unstainable granule (food granule or ferment). 



2. A darker-staining zone, generally containing darker granules (somo- 

 sphere with centrosomes). 



3. A lighter, irregular zone (centrosphere). 



4. A darker, granulated zone (granosphere). 



5. A lighter, unstainable zone, not always distinguishable (hyalosphereV 



6. An outer, fringed zone (plasmosphere), stainable with eosin. 



IX. Blood-Plates and Plasmocytes. 



From the above description it becomes apparent that the 

 blood-plates of the human blood show a very great similarity 

 to the plasmocytes of the blood of Batrachoseps. In many 

 instances, indeed, the structure is identical even to the minutest 

 details. A comparison of the various figures given in this paper 

 with PL II, Figs. 57, 60, 80, 81, etc., of my former paper ('97), 

 shows this similarity to be so great as to leave no doubt as to 

 the indentical nature of the blood-plates and the plasmocytes. 



The prominent, inner, refractive body or bodies in the blood- 

 plates are also seen in many of the plasmocytes. I have sug- 

 gested that these refractive bodies may constitute food granules 

 or secreted matter, and I think they are entirely distinct from 

 the centrosphere (/. c, p. 10). Among the dark-staining struc- 

 tures of the blood-plates we meet with zones corresponding to 

 the centrosomes, somosphere, centrosphere, and granosphere of 

 the plasmocytes ; but the minuteness of the blood-plates is 

 such as to make a segregation of these zones most difficult, 

 even under favorable circumstances, and in most instances it 

 is impossible. There is, however, no doubt but that the inner 

 dark-staining granules, which frequently occur in groups of three, 

 must be identified as centrosomes, having the same nature, 

 appearance, and staining qualities as the centrosomes in the 



