70 CICATRIZATION OF WOUNDS 



In other words, if the wound no. 221 (Fig. 12) has shrunk 

 by 5 '5 square centimetres in four days, between the 17th 

 and 2 1st of December, and if another wound no. 263 has 

 diminished by 20 square centimetres (from no to 90 cm. 2) 

 it is not certain that it is the first one which has been the 

 slower to cicatrize. In the first case, the initial surface was 

 16.2 cm.2 (previous to that it was infected); 5-5 cm.^ therefore 

 represents about one third of the total area of the wound; 

 whereas, in the case of no. 263, 20 square centimetres corre- 

 spond to one fifth of the area. It is the smaller one, therefore, 

 which healed quicker. 



As a consequence it was quite natural to express the 

 quantity cicatrized as a fraction of the work accomplished 

 with respect to the total work to he accomplished^ that is to say, 

 in relative units. To do this it sufficed to divide the area 

 cicatrized in a given time, by the total area at the beginning of 

 the experiment. 5 being the initial surface at the moment 

 when infection, one of the principal causes of delay, has been 

 eliminated, and S' the surface at the end of a time t (expressed 

 in days), the work accomphshed with respect to the total 

 surface vS will be: 



^=^ (I) 



In the examples cited, the value of this ratio is 5-5 : i6-2 = 

 034 for the first and 20 : no = o-i8 for the second, in round 

 figures. Experience soon showed that a small wound will, 

 in all cases, heal relatively quicker than a large one. The 

 surface of the wound seemed thus to play a primary part. 



On the other hand, it was necessary to introduce time into 

 our formula in order to express the quantity cicatrized per 



S—S' 

 day. This was done by dividing the quotient — - — by r, 



number of days elapsed between the measurement of the 

 area 5 and the measurement of area S\ just as one divides the 

 number of miles by the time, to obtain the mean velocity of 

 a distance travelled. The formula became then: 



