f public sentiment may oblige him to do his part in case he
does not do it of his own free will.

+Control of Infectiousness by Treatment--Importance of Salvarsan.+--In a
disease which yields so exceptionally well to treatment as syphilis, a
great deal can be done to shorten the contagious period. Especially is
this so when we are able to employ an agent such as salvarsan, which
kills off the germs on the surface within twenty-four hours after its
injection. When a patient is discovered to be in a contagious state, in
a large majority of cases the risk to the community which he represents
can be quickly eliminated, at least for the time being. Combining the
use of mercury and salvarsan in accordance with the best modern
standards, the actively contagious period as a whole can be reduced in
average cases from a matter of years to one of a few weeks or months.
Certainly, so far as recognizable dangerous sores are concerned,
periodic examination, with salvarsan whenever necessary, would seem to
dispose of much of the difficulty.

+Obstacles to Control by Treatment.+--There are, however, obstacles in
the way of complete control of infectiousness by treatment. For example,
one might ask whether a single negative blood test would not be
sufficient assurance that the patient was free from contagious sores. It
is, however, a well-recognized fact that a person with syphilis may
develop infectious sores about the mouth and the genitals even while the
blood test is negative. An examination, moreover, is not invariably
sufficient to determine if a patient is in a contagious state. The value
of an examination depends, of course, entirely on its thoroughness and
on the experience of the physician who makes it. It is only too easy to
overlook one of the faint grayish patches in the mouth or a trifling
pimple on the genitals. The time and special apparatus for a microscopic
examination are not always available. Moreover, contagious lesions come
and go. One may appear on the genitals one day and a few days later be
gone, without the patient's ever realizing that it was there--yet in
this interval a married man might infect his wife by sexual contact. The
patient with a concealed syphilis often lacks even the incentive to seek
examination by a doctor. It is important also to realize that when
mercury has to be the only reliance, the risk of infection cannot be
entirely controlled by treatment. Contagious sores may develop even
during a