Graphic representation of the cicatrisation of a wound was obtained in the following manner. Time was represented in abscissae and surface in ordinates. Curves were thus obtained which enabled one, day by day, to estimate the variations of the surface and those of the cicatrix. Thus the parts taken by connective and epithelial tissues in repair may be observed.

The investigations of Carrel have shown that the curve of cicatrisation thus established is geometrical in form. Lecomte de Nouy has recently determined the algebraic expression of this curve.1 Nouy's formula consists of two equations -

1 Carrel, Journal of the American Medical Association, 1910, and Journal of Experimental Medicine, 1916. Lecomte du Nouy, Journal of Experimental Medicine, Nov. 1916. A. Hartmann, These de Paris, 1916.

s - s'/s

(I) s/(t+√T)=i

(2) s"= s'(1 - i(t' +√T +t)) s is the total surface of the wound on the day of commencing the observation; s' is the surface of the wound t days later, at the time of the second observation (usually four days later, so that the cicatrised area s - s' shall be sufficiently important); t is the time elapsing between the two first observations;

T is the "age" of the wound, reckoned from the time of the first observation s; so that in the first equation T = t; t' is the time which must elapse between the day of the last observation s', and the day for which it is desired to calculate the theoretical area of the wound; i is a coefficient characteristic of each wound, on the determination of which the formula is based.

Thus we see, by the mere examination of the two equalities (1) and (2), that the former tends to establish a certain index of cicatrisation i, which is then introduced into the latter, in order to calculate the surface of the wound at any given time.

The index i is obtained by means of the formula (1) after two observations made at four days' interval when the wound is aseptic. Experiment has shown that this index is a function of the age of the wounded man, and also of the surface of the wound, and that it is larger in proportion as the latter is smaller, and the patient younger. Lecomte du Nouy establishes a curve which makes the previous calculation of the index unnecessary (Fig. 8). The only elements needed for the calculation of this curve of cicatrisation are the area of the sterile wound and the age of the patient.

By means of two observations made at four days' interval, or even by means of a single observation, the age of the patient being known, it was possible to calculate the theoretical curve of cicatrisation. On the same sheet the course of the observed curve was plotted (Fig. 9). It was thus possible to ascertain the abnormal variations of the rate of repair to be observed in the wound, these manifesting themselves by the divergence of the observed curve from the calculated curve. Fig. 8. - Cicatrisation curve of an aseptic wound. Surface, expressed in square centimetres, forms the ordinates, whilst time, in days, the abscissae. (Case 221.) Fig. 9. - Curves, observed and calculated, for the same wound. By means of observations made the 17th and 21st of Dec, the progress of cicatrisation was calculated according to the formula of Lecomte du Nouy. A continuous line represents the observed curve, and a dotted line the calculated curve. The coincidence of the two curves is almost perfect. (Case 221.)

As we possessed also the chart of the bacteriological condition of the wound, it was easy to estimate almost exactly the part played in the progress of repair by the substance under examination. By means of this method the action of hypochlorite of soda upon the repair of wounds was examined. Experiments were successively made upon infected wounds, and upon those surgically sterile, that is to say, wounds whose secretions examined by means of "smears" no longer contained microbes. Fig. 10. - Cicatrisation curve of a wound of the abdominal wall. Slowing down of cicatrisation from Feb. 10th to Feb. 18th, due to a re-infection. Acceleration from Feb. 18th to Feb. 22nd, under the influence of Dakin's solution. (Case 327.) Fig. 11. - Curve indicating the bacteriological condition of the preceding wound from Feb. 4th to Feb. 21st. The slowing down of cicatrisation coincides with a re-infection of the wound which reached its maximum Feb. 16th, and the acceleration coincides with the sterilisation which occurred Feb. 18th. (Case 327.)