CHEMICAL CLOCK 



169 



Young and old, united in the same space, live in a separate 

 universe where the value of time is radically different. Peda- 

 gogues and psychologists do not seem as yet to have taken 

 into account the considerable importance of this disaccord. 

 Obviously, the manner in which this could be done is by no 

 means evident. But this is another problem. 



'A 



V/AAA 



p p □ n 



Q hyperbola 

 Constant ^ 



^ 



\';^^ M \mA VM \^fzi 



10 



20 



30 



uo 



50 



60 



JO Aje 



FIG. 31. RELATIVE VALUES OF OUR APPRECIATION OF THE DURATION 

 OF ONE SIDERAL YEAR, COMPUTED FROM THE CONSTANT "^A' (SECOND ROW), 

 Al^ID FROM THE HYPERBOLA (FIRST ROW), WITH RESPECT TO THE AGE 



OF TWENTY TAKEN AS REFERENCE 



Thus there is a physiological time which has no signification 

 excepting for organisms capable of being born, of ageing, and 

 of dying normally. This word 'normally' contains in sub- 

 stance the greater part of unsolved biological problems. It 

 implies, for instance, the action of the organic regulating 

 mechanisms which establish the fundamental difference 

 between the healthy normal growth of cells and the abnormal, 

 anarchical growth of cancerous cells, between an immortal 

 tissue- culture and an individual who is born, lives, and dies. 



Between a malignant tumour and a healing wound which 

 cicatrizes by rapid cellular proliferation let loose in the heaJthy 

 tissue by the wound itself there is, barring the morphological 

 difference of the cells, only the following difference: prolifera- 

 tion stops instantaneously when reparation is ended in a 

 healthy flesh, whereas a cancerous tissue ignores this regu- 

 lating mechanism and continues to proliferate until death 

 follows. Similarly, when a tissue-culture is cut in two and 

 placed in a fresh drop of nutritive medium after washing, the 

 cells, which proliferate slowly in the organism, are taken with 

 a frenzy of growth and reproduce with great rapidity. We 

 have seen that a tissue-culture two square millimetres in size 

 doubles its volume in forty-eight hours indefatigably and 



