ce-area
of a wound, with time expressed in days, measured from the time when the
wound is aseptic or sterile. When this aseptic condition is reached, by
washing and flushing continually with antiseptic solutions, two
observations at an interval commonly of four days give the 'index of the
individual,' and this index, and the two measurements of area of the
wound-surface, enable the physician-scientist to determine the normal
progress of the wound-surface, the expected decrease in area, for this
wound-surface of this individual. The area of the wound is traced
carefully on transparent paper, and then computed by using a mathematical
machine, called a planimeter, which measures areas.

"The areas of the wound are plotted as ordinates with the respective times
of observation measured in days as abscissas. After each observation and
computation of area the point so obtained is plotted to the same axes as
the graph which gives the ideal or prophetic curve of healing.

"When the observed area is found markedly greater than that determined by
the ideal curve, the indication is that there is still infection in the
wound.... A rather surprising and unexplained situation occurs frequently
when the wound-surface heals more rapidly than the ideal curve would
indicate; in this event secondary ulcers develop which bring the curve
back to normal....

"This application of mathematics to medicine is largely due to Dr. Alexis
Carrel of the Rockefeller Institute of Medical Research. He noted that the
larger the wound-surface, the more rapidly it healed, and that the rate of
healing seemed to be proportional to the area. This proportionality
constant is not the same for all values of the surface or we would have an
equation of the form,

_S = S__1__e__-kt_

in which _S_, is the area at the time that the wound is rendered sterile
and observations to be plotted really begin....

"The data given are taken from the Journal of Experimental Medicine,
reprints kindly furnished by Major George A. Stewart of the Rockefeller
Institute. The diagrams are reproduced from the issue of Feb. 1, 1918, pp.
171 and 172, article by Dr. T. Tuffier and R. Desmarres, Auxiliary
Hospital 75, Paris....

[ A graph, showing the progress of healing of a surface wound of the right
leg of a 31-year-old patient. It shows that as time passes, the wounded
area decreases. ]

Progress of healing of a surface wound of the right leg, patient's age 31
years.

"WAV