CHICKEN BONE MARROW IN PLASMA MEDIUM 91, 



which is already present after 24 hours of incubation. Now 

 Foot ('12, p. 459, fig. 5) gives the photograph of a preparation 

 of bone marrow after 5 days of incubation in a plasma medium. 

 This is a descrepancy for which no explanation could be found. 



It is of importance to state that all vacuoles do not contain 

 fat in such a condition as to make it visible by the osmium 

 process. The cell (fig. 32) shows still some fine traces of fat, 

 but in many preparations which were treated with Scharlach 

 or Sudan stain after adequate fixation, the vacuoles were devoid 

 of fat. It is conceivable that fatty acids or other products of 

 related character fill the vacuoles, but even after trying the 

 most complicated stains (Ciaccio, Benda) to elucidate the 

 nature of the contents in the vacuoles, no final decision could 

 be I'eached. 



From the third to the fifth day, the number of 'Riesenzellen' 

 has diminished; we see smaller round or oblong cells with one 

 or several vacuoles, with oblong faintly chromatic nuclei (fig. 

 34). They are the products of the breaking up of the 'Riesen- 

 zellen' and seem to be identical with Foot's cell culture type. 

 They are capable of phagocytosis and move slowly toward the 

 periphery of the plasma clot. 



How can we interpret these extraordinary changes in the 

 fat cells? The only similar observation was made by Maximow 

 ('04, p. 108), describing the changes occurring in the cells of 

 inflamed connective tissue of the rat. There he gives a good 

 description of the involution of the fat cells. The process 

 shows the same phenomena in the involution of the fat cells 

 in the connective tissue of the living animal after inflammation 

 as are to be seen in tissue culture. The flattening out of the 

 cytoplasm, the dividing up of the big fat globule into small 

 droplets inside the cell (Maximow, plate 3, fig. 9; Erdmann, 

 text-fig. A) and the transformation of the plasma in a honey- 

 combed mass (Maximow, Plate 3, fig. 11; Erdmann, fig. 7, left 

 side, above), are identical processes in both cases. Maximow 

 believes ('04, p. 119) that some of these cells become fibroblasts. 

 The present author ventures no opinion on the subject, though a 

 striking similarity exists between the fibroblasts of Maximow 

 (text-fig. B) and the cell in figure 7, right side above. 



