ess for others. Just as every syphilitic runs a gradual
course to a tertiary period, so every syphilitic in time becomes
non-contagious, almost regardless of treatment.

+The Time Element in Contagiousness.+--It is the time that it takes an
untreated case to reach a non-infectious stage and the events or
conditions which can occur in the interval, that perpetuate syphilis
among us. The chancre is contagious for several weeks, and few
syphilitics escape having some contagious secondary lesions the first
year. These are often inconspicuous and misunderstood. They may be
mistaken for cold sores or the lesions about the opening of the rectum
may be mistaken for hemorrhoids, or piles. The recurrence of these same
kinds of sores may make the patient dangerous from time to time to those
about him, without his knowledge. It is an unfortunate thing that the
most contagious lesions of syphilis often give the patient least warning
of their presence in the form of pain or discomfort. While they can
often be recognized on sight by a physician, it is sometimes necessary
to examine them with a dark-field microscope to prove their character by
finding the germs. It is a safer rule to regard every open sore or
suspicious patch in a syphilitic as infectious until it is proved not to
be so.

+Contagious Recurrences or Relapses.+--The duration of the infectious
period in untreated cases and the proportion of infectious lesions in a
given case vary a good deal and both may be matters of the utmost
importance. Some persons with syphilis may have almost no recognizable
lesions after the chancre has disappeared. Others under the same
conditions may have crop after crop of them. There is a kind of case in
which recurrences are especially common on the mucous or moist surfaces
of the mouth and throat, and such patients may hardly be free from them
or from warty and moist growths about the genitals during the first five
years of the disease, unless they are continuously and thoroughly
treated. Irritation about the genitals and the use of tobacco in the
mouth encourage the appearance of contagious patches. Smokers, chewers,
persons with foul mouths and bad teeth, and prostitutes are especially
dangerous for these reasons.

+Average Contagious Period.+--It is a safe general rule, the product of
long experience, to consider a person with an untreated[10] syphilis as
decidedly infectious for the first three years of his disease, and
somewhat so th