THE MITOTIC CYCLE 



fact discovered by Fell that solid particles ly. or more in diameter can 

 slowly be phagocytosed by fibroblastic cells, the growth of which is not 

 impaired by the presence of these foreign inclusions. Once within a cell, 



120 



100 



90 - 



•^^ 10 



H 



off\ ^.- 



\^f-^: 



I on 



•N 



N 



of\ 



r 



\ 



'^j 



i;*"*"^- 



Seconds 



Figure 6 Angular displacement of a magnetic particle in the cytoplasm of a 



chick osteoblast in culture when magnetic fields of a 8 oersteds, b i6 oersteds 



were applied for the intervals indicated. From Crick and Hughes*' 



{By courtesy. Academic Press Inc. New Tork). 



a magnetic particle can be rotated by two magnetic fields at right angles 

 to each other in the apparatus used by Crick and Hughes. First one field 

 is used to orientate the particle, and then the other is applied for a vari- 

 able interval. Cells containing particles were rigorously selected to mini- 

 mize disturbing influences by neighbouring structures and inclusions. 



m 



^60 



M 



OS 

 I 

 t. 



/\ 



/: \ Or 



f H 



Off 



I 



4 



Off 



I 



i \ On 



\J'^ 



/ 



t 



On 



\ n 



\. i On 



V 



I 



Off 



I \ I 



\ J On 



\ 



1 



Off 



J L 



I I I I L 



\ 7 On 

 \i 

 I 

 Off 



J_J I \ 1 L 



V 



10 12 It 



Time 



22 Zf 2B 

 Seconds 



Figure 7 Increase in angular displacement of a magnetic particle in the cytoplasm 



of a chick osteoblast in culture when a magnetic field of 24 oersteds was applied 



alternately in opposite directions. From Crick and Hughes^" {By courtesy, 



Academic Press Inc., New Tork). 



26 



