tion takes place during the congress
of the sexes. Delicate, easily abraded surfaces are then brought into
contact, and the discharge from lesions containing the virus is placed
under favourable conditions for conveying the disease from one person to
the other. In the male the possibility of infection taking place is
increased if the virus is retained under cover of a long and tight
prepuce, and if there are abrasions on the surface with which it comes
in contact. The frequency with which infection takes place on the
genitals during sexual intercourse warrants syphilis being considered a
venereal disease, although there are other ways in which it may be
contracted.

Some of these imply direct contact--such, for example, as kissing, the
digital examination of syphilitic patients by doctors or nurses, or
infection of the surgeon's fingers while operating upon a syphilitic
patient. In suckling, a syphilitic wet nurse may infect a healthy
infant, or a syphilitic infant may infect a healthy wet nurse. In other
cases the infection is by indirect contact, the virus being conveyed
through the medium of articles contaminated by a syphilitic
patient--such, for example, as surgical instruments, tobacco pipes, wind
instruments, table utensils, towels, or underclothing. Physiological
secretions, such as saliva, milk, or tears, are not capable of
communicating the disease unless contaminated by discharge from a
syphilitic sore. While the saliva itself is innocuous, it can be, and
often is, contaminated by the discharge from mucous patches or other
syphilitic lesions in the mouth and throat, and is then a dangerous
medium of infection. Unless these extra-genital sources of infection are
borne in mind, there is a danger of failing to recognise the primary
lesion of syphilis in unusual positions, such as the lip, finger, or
nipple. When the disease is thus acquired by innocent transfer, it is
known as _syphilis insontium_.

#Stages or Periods of Syphilis.#--Following the teaching of Ricord, it
is customary to divide the life-history of syphilis into three periods
or stages, referred to, for convenience, as primary, secondary, and
tertiary. This division is to some extent arbitrary and artificial, as
the different stages overlap one another, and the lesions of one stage
merge insensibly into those of another. Wide variations are met with in
the manifestations of the secondary stage, and histologically there is
no valid distinction to b