CHICKEN BONE MARROW IN PLASMA MEDIUM 79 



nuclei spherical and very often dividing. It is impossible to 

 define without doubt the exact type of these granulocytes before 

 the relation of their granules to basic or acid stains develops 

 the true character of these cells. Therefore we do not venture 

 any interpretation of the bigger type of these granulocytes but 

 point out only that the smaller forms must be eosinophil leuco- 

 C3'tes after their morphological structure, though their granules 

 appear rather darker than those in non-incubated leucocytes of 

 chicken-bone marrow. Also they have less distinctly round or 

 less rod-shaped granules. These two observations are important. 

 The big cell in the center of the figure 2 does not contain any 

 granules but is from the large nongranular mononuclear lympho- 

 cyte type. Very often these cells break into pieces during ob- 

 servation. 



Two other cells, one on the right, the other on the left side of 

 figure 2 are of a different type They contain large shining 

 droplets, the fatty nature of which seems doubtless. Their 

 nuclei have a vesicular structure and appear at this stage of the 

 culture as often dividing. They are less numerous than the 

 eosinophil leucocytes which form, in the first 24 hours, the bulk 

 of all cells migrating into the surrounding plasma medium. 



Figure 3 represents bone marrow which has been incubated 

 for 48 hours (January 3 to January 5, 1916). Here a 'Riesen- 

 zelle' is rapidly moving; its cytoplasm is spread over a great 

 area on the cover-glass and contains fat droplets and glisten- 

 ing granules. This ' Riesenzelle' shows in its cytoplasmic 

 structure a close resemblance to the fat droplet containing cells 

 on figure 2. To account for the larger size, we can either sup- 

 pose that several of these cells have fused together or the cyto- 

 plasm of a single cell is thinned out by the method of cultivation. 



The structure of the granulocytes is not very much changed. 

 The larger forms with glistening granules and half-moon-shaped 

 nucleus have diminished in number but smaller cells of the same 

 type can be discovered now and then. In these forms some- 

 times fat droplets are visible. The eosinophil leucocytes are 

 still abundant, but are surpassed in number by small ungranu- 

 lated cells. These form now the bulk of the cells migrating into 



