BONE. 69 



same structure and character as the lymph-cells, and 

 called, par excellence, marrow-cells ; 3. cells some- 

 what larger than the last mentioned, with, usually, a 

 single very irregular-shaped and sharply defined nu- 

 cleus ; 4. very large granular cells, which usually 

 have several nuclei scattered through the cell-body, 

 or grouped on one side, the so-called myeloplaxes or 

 giant cells. It is not improbable that the two last 

 varieties are only modified forms of the same kind 

 of cells. In the marrow of developing bone are seen 

 spheroidal, or irregularly cuboidal, large granular 

 cells, with commonly oval nuclei, usually situated 

 at one side of the cell-body. These are the so-called 

 osteoblasts, with which we shall become better ac- 

 quainted when we study the process of bone 

 development. 



In addition to the above cell-forms, red blood- 

 cells, escaped from the blood-vessels, are usually 

 seen in abundance. Not infrequently, when fresh 

 marrow is studied, cells are seen which in many 

 respects are like the true marrow-cells, but which, 

 with a distinct nucleus, have a homogeneous cell- 

 body resembling in its color the red blood-cells. 

 These cells are the so-called nucleated red blood-cells, 

 and are believed by some observers to be destined 

 to lose their nuclei and assume the character of the 

 ordinary red blood-cells. Those who advocate this 

 view regard the marrow of bones as one of the 

 blood-producing tissues of the body. The trans- 



