INFLUENCE OF SIZE OF WOUND lOI 



I have dwelt at length on the details of these calculations 

 and have taken the reader 'behind the scenes', a thing which 

 by tradition or modesty the scientist usually avoids, because 

 it was necessary that he should have absolute confidence in the 

 results published. This confidence can only be acquired in 

 three ways. By repeating the experiments, by knowing the 

 author personally, or by possessing as many elements as 

 possible to enable one to follow step by step all the reasonings 

 which have led to the final conclusion. The two first methods 

 were difficult of realization, and I was therefore obliged to have 

 recourse to the third. 



In order to define more clearly the notion of time and the 

 mechanism of ageing in certain biological processes as well as 

 to check the results obtained in vivo, we shall now study the 

 admirable method of tissue-culture outside the organism, 

 which Carrel established in 1912 at the Rockefeller Institute 

 of New York. I shall be obliged to dwell on it at length, for 

 this method has made it possible to detect the existence of the 

 chemical changes underlying the process of ageing, and also 

 to understand the accumulative processes registering the flow 

 of time. It is therefore a new and indispensable element for 

 our ulterior reasoning. 



