98 RHODA ERDMANN 



(figs. 8, 35, 36 and 37) after leaving the bone marrow network, 

 can form 'Riesenzellen' which by their nuclear structure resemble 

 connective tissue cells. They later become the cells to which 

 Foot gave the name ''cells of the cell culture type." They are 

 enlarged, fat-storing or vacuolized cells capable of phagocytosis. 



The results here presented, i.e., the change of the small vesicu- 

 lar basophil cell into true phagocytes and later into 'Riesenzellen' 

 or cells of the cell culture type — were attained by using the bone- 

 marrow of a young, fat-less chicken and the washing out of the 

 undesired cell types, as polymorphonuclear leucocytes. But even 

 if we use the fatty bone-marrow of a full-grown chicken and con- 

 trol the daily changes, the same fact is demonstrated. The first 

 day after incubation (fig. 7) we observe a large number of baso- 

 phil mononuclear lymphocytes. Three are shown in one micro- 

 scopic field. Their pale nuclei, often of a lighter blue than the 

 plasma, the irregular shape of their plasmatic body in which 

 sometimes a few fine -acidophil granules are visible, and their 

 large size, make them conspicuous. Examining preparations of 

 the same series a day later, the lymphocytes are very scarce. 

 On the fifth day of incubation, when the disintegrated fat has 

 been disposed of by the phagocytic acti\dty of these basophil 

 cells, characterized by their close position to the network of the 

 bone marrow, they are by far the most numerous types in our 

 tissue cultures. In the following days they grow and divide 

 rapidly forming 'Riesenzellen' which can store fat, become vacu- 

 olized, and end in rounding off and becoming cells of the cell 

 culture type, their nuclei with a fine thread-work of chromatin 

 becoming more like true connective tissue nuclei. They can 

 even lose their basophily but may always be distinguished by 

 their nuclear structure from the products of the regressive de- 

 velopment of the eosinophil leucocyte in tissue cultures. 



It might be possible to interpret Foot's text-figure 5, (page 459, 

 '12) as representing a tissue culture preparation just in such a 

 stage; because the time for formation of these features is the 

 same. But then it is not explained why Foot does not describe 

 the formation of the 'giant cells' and cells of 'cell culture' type 

 after 24 hours' incubation. 



