2:).s 



iiif^ Hk' cells niid cNpcllin^ llu-m on a covor-slij), on which 

 Ihcrc is a clroj) of IVcsh plasma and omlji'vonic tissue juice. 

 By this method, it was ])ossil)le to ol)(ain hundreds of 

 isolated cells on one slide. 



The observations were made under the hii^h power mi- 

 croscope, which was placed in a special heating box, in 

 order to keep the cultures at body-temperature during 

 observation. 



It rc(iuired much patience to keep on observing these 

 cells for hoiH's under the high powei' lenses. It was vej'v 

 tiresome and often rather disa])poinling, because of the 

 many cells and cell-groups, which were found unsuitable 

 for these obsei'\'ations. 



The various typical changes of the cell-shape were im- 

 mediately drawn on paper. Sometimes, however, the move- 

 ments were so lively, that it was almost imjjossible to make 

 the drawings fast enough during the observation. In these 

 cases, micro-cinematographic recording would have been 

 of excellent use and would fiave given W'Onderful infor- 

 mation. 



It can be generally stated thai almost in all cultures 

 that could be observed, the sarcoma cells were able to 

 divide independently, when they were isolated and scat- 

 tered. The mechanism of the cell division of the sarcoma 

 cells was so entirely different from that of the normal 

 tissue cells in vitro, that mitotic cell division was very 

 seldom observed in the cultures of sarcoma cells. 



The cells which were seen growing out from the ex- 

 planted piece of the Rous chicken sarcoma, were extremely 

 polymorphous. The sizes of the various t3'pes of cells were 

 innumerable. The smallest of the cells w^ere about the 

 size of big bacteria or blood-platelets and the largest al- 

 most 50 — 150 times larger than the smallest. The type of 

 small ameboid cells and the type of the medium-sized 

 were far the most active of all the cells. The big cells, 

 almost giant cells, were usually very slow in movement 



