In 1909, Ehrlich determined, after a series of laboratory experiments on
animals inoculated with the syphilis germ (spirochæta pallida), that a
complex compound, with arsenic as its base, had the desired effect of
destroying the parasite, in a dose not poisonous to the animal. This
compound, first designated as "606," representing its number among his
many laboratory experiments, he later named "salvarsan." With the
assistance of his clinical friends, he soon demonstrated the action of his
compound on man, and gave it freely to the world. Although it is now
almost universally used, it has not proved to be the absolute cure that it
was hoped it would be, as some of the spirochætæ seem to be hidden away
where they are protected from the circulating poison,--to bring forth new
progeny,--thus producing so-called recurrence.

The possibility of the infection of innocent persons is always uppermost
in the mind of the medical man, and should equally concern the layman.
Contaminated articles and utensils, such as towels and common
drinking-cups, have caused many infections. This danger is greater from
syphilis than from gonorrhea, for the reason that the spirochæta pallida
is more virulent than the gonococcus. In our own fields, camps, and mines,
it is common for men to drink from one jug or dipper. Infection almost
surely follows if one of the crowd has a syphilitic sore on the lip. So
intense is the activity of the spirochæta pallida in the primary stage
that it may be borne to innocent parties by unwashed clothes and utensils
of any kind, that have been in recent contact with a primary syphilitic
sore. A dentist's or a doctor's instruments, for instance, are extremely
dangerous as infection carriers, if they are not thoroughly sterilized by
boiling. The danger of infection in syphilis and gonorrhea depends largely
upon the virulence of the individual infection. As some living tubercle
bacilli may be harbored and thrown off with impunity, while others will