A BIOLOGICAL PHENOMENON 55 



practitioners who had been obliged to transform themselves 

 instantaneously into surgeons, and who often found themselves 

 brutally faced with important lesions for the immediate treat- 

 ment of which they possessed scant information, and no 

 training. 



The expenses of the laboratories of Temporary Hospital 21 

 were supported by the Rockefeller Institute of New York. 



Dr. Carrel asked me one day what method could be 

 employed for measuring exactly the surface of any kind of 

 a plane area. In fact, he was interested in estimating the surface 

 of wounds which he was studying with Dr. Alice Hartmann, and 

 which v/ere outhned on cellophane by means of a wax pencil 

 or even a fountain pen. He told me that up till then he had 

 employed the weighing method, which consists in transferring 

 the first drawing obtained directly on the wound on to a sheet 

 of paper, which is then cut out following the lines of the 

 drawing as exactly as possible, and weighed. 



Figures proportional to the areas of the wounds are thus 

 obtained on condition that the paper utilized is always of the 

 same thickness. He explained the inconveniences of this 

 technique, which was delicate, lengthy, and inaccurate. I sug- 

 gested employing the planimeter, an instrument well known 

 to engineers, which enables one to evaluate in a few minutes, 

 with precision, the area of any surface in square centimetres. 

 The problem which was occupying Dr. Carrel at the time was 

 the following one. He had been able to convince himself that 

 the cicatrization of surface wounds maintained under proper 

 conditions evolves according to a geometric law. This 

 phenomenon had not been studied quantitatively, owing to the 

 fact that its only interest before the war was a purely physio- 

 logical one. Furthermore, in order to solve it, some notion 

 of mathematics was necessary and, at that time, mathematical 

 culture was not generally found amongst biologists. Carrel 

 thought that I might succeed and asked me to study the 

 question. He believed that the solution would solve rapidly 

 and without possible discussion, the question of the relative 

 value of the different treatments proposed for the dressing of 



