ally understood. In many cases it is possible, especially early in
the disease, by a few rubs of mercurial ointment, or a few injections of
mercury, or even in some cases by the use of pills or liquid medicine,
to make a positive blood test for syphilis negative. But this negative
test is only temporary. Within a short time, usually after treatment is
stopped, the test becomes positive again, showing that the mercury has
not yet cured, but simply checked, the disease, and that it may at any
time break out again or do internal damage. It must be understood that a
negative blood test just after a patient has been taking mercury _has no
meaning_, so far as guaranteeing a cure is concerned. It is only the
blood test that is repeatedly negative after the effect of mercury wears
off, which shows the disease is cured. Yet many a syphilitic may and
does think himself cured, and may marry in good faith, or be allowed a
health certificate, only to become positive again. He may then develop
new sores without his knowledge even, and perhaps infect his wife, or
may himself in later years develop some of the serious consequences of
the disease.

Whenever one talks to a person who knows something about the advances in
knowledge in the past few years about the treatment of syphilis, and
goes into detail about mercury, the odds are two to one that he will be
interrupted by the question, "But what about '606'?" Before talking
about salvarsan, or "606," it is well to say here that this new drug,
wonderful though it is, has in no sense done away with the necessity for
the use of mercury in the treatment of syphilis. Mercury has as high a
reputation and is as indispensable in the cure of syphilis today as it
was four centuries ago. It has as yet no substitutes. We appreciate
every day, more and more, how thoroughly it can be depended on to do the
work we ask of it.[8]

[8] A drug known as the iodid of potash (or soda) is widely used in
the treatment of syphilis, and especially of the late forms of the
disease, such as gummas and gummatous sores. It has a peculiar
effect on gummatous tissue, causing it to melt away, so to speak,
and greatly hastening the healing process. So remarkable is this
effect that it gives the impression that iodids are really curing
the syphilis itself. It has been shown, however, that iodids have no
effect on the germs of syphilis, and therefore on the cause of the
disease, altho