80 RHODA ERDMANN 



the surrounding plasma clot from the implanted tissue particle. 

 They have either vesicular, less refractive or very shining and 

 highly refractive nuclei. 



In plate 2 we can follow in detail the further changes of the 

 'Riesenzellen.' The bone marrow (fig. 4) has been implanted 

 72 hours, from January 3 to January 6, 1916. Three round 

 cells with big fat droplets can be seen, which seem to protrude 

 out of the cell or cover its surface. The nuclei are therefore 

 very seldom visible. When visible, they appear dark. A few 

 granules are contained in the cytoplasm besides round or ir- 

 regularly shaped masses, which seem to be remnants of other 

 cells. On the third day after implantation these cells im- 

 mediately attract the attention of the observer. They seem 

 to have taken the place of the 'Riesenzellen;' this could 

 be demonstrated by observation of the living cells. Some 

 ' Riesenzellen' break apart, take on a round shape and com- 

 pletely extrude the fat droplets. These may be small or larger 

 (fig. 5, second cell, left side) and show very fine pseudopodia. 

 They are round cells which can survive an indefinite time in 

 the plasma medium, the so-called 'cell culture type.' 



Many 'Riesenzellen' however (fig. 5), the similarity of which 

 to the round cells seen in figure 4 can be easily discovered, show 

 all signs of degeneration. The cytoplasm has a 'curdled' 

 appearance and is torn. The fat droplets have been thrown out 

 into the plasma clot, and the granules have acquired a dark 

 appearance. This regressive process takes place on the fourth 

 or fifth day after implantation. These decaying cell masses 

 are surrounded by small ' granulated and ungranulated cells 

 and seem to be able to phagotise, because their cytoplasm shows 

 in some places 'curdled granules.' 



During the next days of incubation, no striking changes take 

 place. The number of living cells diminishes and few tjrpes 

 of cells are in healthy condition. 



Fig. 6 shows cells which have been incubated in the same 

 plasma medium 216 hours (from December 25 to January 3). 

 They have small distended nuclei which do not seem to contain 

 much chromatin, and the cytoplasm is filled with shining 



