INFLUENCE OF SIZE OF WOUND 93 



cicatrization direcdy, without passing by intermediary points. I 

 had to proceed point by point. It was an extrapolation formula. 



I spent several weeks in search of the ideal general equation. 

 By 'ideal' I mean that it must not have more than two co- 

 efficients and that these coefficients must necessarily be func- 

 tions of the index i^ which had a well-determined significance 

 and was itself a function of the age of the patient. I was 

 especially anxious to obtain these coefficients without calcula- 

 tion, by means of a chart. It was necessary that they should 

 not be arbitrary. It is always possible with a littie patience to 

 find an equation by increasing the number of arbitrary co- 

 efficients. But the interest of a formula is then much sHghter. 

 A little farther on I will mention such a case. 



Mr. de Rufz de Lavison, to whom I exposed my difficulties, 

 agreed to collaborate with me in this work. A few weeks later 

 he brought me an equation which was satisfactory from the 

 point of view of the accord with the observed facts. Unfortu- 

 nately it contained two coefficients which I could not connect 

 with the values of /. This equation was the following: 



T=k,l.og,^^+2k,WS~VS). 



It can be seen that it gives the time elapsed T instead of the 

 area of the wound. To obtain the date of total cicatrization it 

 sufficed to replace vS by 0-4 or 0-3, and Twas obtained in days. 

 This result encouraged me to take up my calculations anew 

 in another way, and this is how I attempted to do it. 



Let us admit that during a very short time dt (the differ- 

 ential notation is here employed) the cicatrized area ds remains 

 proportional to the total area. This is written in the following 

 way: 



-ds^KSdt 

 from which by integration with respect to time one obtains: 



/ KS 



