BONE-MARROW 223 



tion is extensive, lends weight to this hypothesis. Likewise Badertscher 

 (Amer. Jour. Anat, 15, 1, 1913) finds that eosinophil leukocytes and 

 free eosinophilic granules are very abundant in the vicinity of degenerat- 

 ing muscles in salamanders during the time when the gills atrophy, and 

 believes that the eosinophilic granules are ingested fragments of degener- 

 ated muscles and red blood-corpuscles. Eosinophils do undoubtedly in- 

 crease greatly in number during certain infectious diseases characterized 

 by extensive tissue disintegration, e.g., trichiniasis ; but disproof of intra- 

 cellular origin a teaching more in accord with our knowledge of cyto- 

 plasmic granule origin through protoplasmic activity demands direct 

 evidence of extensive granular ingestion, which is lacking. Moreover, 

 the microchemical nature of eosinophil granules differs from that of 

 hemoglobin; also, they differentiate from basophilic granules and in 

 hemogenesis in the turtle, for example, eosinophils appear before hemo- 

 globin-containing cells are present. The free eosinophil granules in 

 degenerating tissues are more likely derived from disintegrating eosino- 

 phils, abundant in such regions. 



6. Basophil Granulocytes (Mast cells). These are identical with 

 the mast leukocytes of the blood, and possibly also with the cells of this 

 name in connective tissue, the latter perhaps representing degenerating 

 phases of the former. They are characterized by a variable polymor- 

 phous nucleus, apparent lack of centrosome, extremely slight prolifera- 

 tive capacity, and presence of spheroidal non-uniform basophilic cyto- 

 plasmic granules. They are numerically increased in marrow and the 

 circulating blood and in the spleen in certain diseases. 



7. Giant Cells or Myeloplaxes. These are relatively enormous 

 cells (of 30 to 100 microns diameter). They may have either a single 

 large, frequently lobulated annular, nucleus (megakaryocyte) or several, 

 even many, nuclei (polykaryocyte). The megakaryocyte is a derivative 

 of the lymphocyte (myeloblast). The polykaryocyte represents a later 

 modification of the megakaryocyte, the lobulated nucleus having become 

 broken up into separate nuclei. These polykaryocytes ('hemogenic giant- 

 cells') have been erroneously regarded as identical with the multinucle- 

 ated osteoclasts. They are in fact potential erythroblasts, comparable to 

 'blood-islands/ with only slight or no phagocytic capacity. After 

 Wright's technic the cytoplasm of these cells presents fine purple gran- 

 ules. Osteoclasts do not contain such 'metachromatic' granules. The 

 polykaryocyte of the yolk-sac of the 10-millimeter pig embryo can be seen 

 to differentiate into erythrocytes, a hemoglobin-containing area developing 

 about the several nuclei, the whole finally breaking up into an equal num- 



15 



