CHICKEN BONE MARROW IN PLASMA MEDIUM 103 



culture of bone marrow. The myelocytes, capable of amoeboid 

 moving, form few 'Riesenzellen.' They can easily be omitted 

 in the following discussion, as they are always distinguished by 

 their characteristic nuclei and the blunt form of their projections, 

 when stained and preserved. They are just as unmistakable 

 when living. The large mononuclear or polymorphonuclear 

 eosinophil leucocytes only need be considered, as X or 'Riesen- 

 zellen' when they have flattened out and formed rays of cells. 

 Then they are surrounded by the projections of the transformed 

 fat cells or cell types of the 'histiotype Wanderzellen' order. 

 Both cell types are true phagocytes, thus forming, chiefly in the 

 first days after incubation, cell masses of X or 'Riesenzellen' of 

 combined characters. The whole combination may even seem, 

 judged only by its acidophil staining, to be from a different 

 origin. But the daily observations reveal the facts of their de- 

 velopment. It is questionable if any necessity exists for giving 

 new names, as Foot did in 1912 and 1913, for the X cells 'Riesen- 

 zellen' and later forms. They are either transformed fat cells, 

 or mesenchymelike wandering cells which have left their custom- 

 ary place and which assume in later life in tissue culture the 

 characters of connective tissue. 



The name 'Riesenzellen' or true giant cells has already been 

 used for cells of the type represented in figure 10. This multi- 

 nuclear cell was seen in a tissue culture of bone marrow from a 

 two-months old chicken, and resembles in every particular the 

 true giant cells figured and described by many authors. 



To call the questioned basophil cells 'X cells' when their ori- 

 gin is known would be a contradiction. They are either 'fat 

 cells' or mesenchymelike cells, and both types are transformed 

 from their original type by our cultivation method. The present 

 author would propose calling the latter simply wandering 

 mesenchymelike cells, and the fat cells, transformed fat cells. 

 Their close relationship to the mesenchymal cell type is again 

 proved by their physiological behavior in tissue culture, so closely 

 identical with that of the wandering mesenchymal type. It 

 even became evident that some 'fat cells' may assume the 

 character of fibroblasts when they are not transformed into 



