particular cells and leave others uncolored and from this starting point
he worked out organic and metallic compounds which would destroy the
bacteria and parasites that cause some of the most dreadful of diseases.
A year after the war broke out Professor Ehrlich died while working in
his laboratory on how to heal with coal-tar compounds the wounds
inflicted by explosives from the same source.

One of the most valuable of the aniline antiseptics employed by Ehrlich
is flavine or, if the reader prefers to call it by its full name,
diaminomethylacridinium chloride. Flavine, as its name implies, is a
yellow dye and will kill the germs causing ordinary abscesses when in
solution as dilute as one part of the dye to 200,000 parts of water, but
it does not interfere with the bactericidal action of the white blood
corpuscles unless the solution is 400 times as strong as this, that is
one part in 500. Unlike carbolic acid and other antiseptics it is said
to stimulate the serum instead of impairing its activity. Another
antiseptic of the coal-tar family which has recently been brought into
use by Dr. Dakin of the Rockefeller Institute is that called by European
physicians chloramine-T and by American physicians chlorazene and by
chemists para-toluene-sodium-sulfo-chloramide.

This may serve to illustrate how a chemist is able to make such remedies
as the doctor needs, instead of depending upon the accidental
by-products of plants. On an earlier page I explained how by starting
with the simplest of ring-compounds, the benzene of coal tar, we could
get aniline. Suppose we go a step further and boil the aniline oil with
acetic acid, which is the acid of vinegar minus its water. This easy
process gives us acetanilid, which when introduced into the market some
years ago under the name of "antifebrin" made a fortune for its makers.