ON THE STANDARDISATION OF ANTI-TYPHOID
VACCINE.

FEW will deny that vaccination against typhoid fever has now taken its place
amongst the measures of preventive medicine. This achievement is princi-
pally due to the brilliant work and the untiring exertions of Wright, who since 1897
has devoted so much time and energy to the various problems which surround
this subject. That success has crowned his efforts is certain from the facts,
(1) that three scientific committees, successively convoked to examine into the
matter, have decided that the statistical evidence is sufficient to show that the
incidence and case mortality are reduced by inoculation, and (2) that the
Germans have adopted it in their army in the case of troops proceeding to
foreign service in Africa. There are still, however, many problems to be solved
before anti-typhoid vaccination becomes generally adopted by all who practise
preventive medicine, and one of the most important of these problems is the
elaboration of some method of standardisation. Before we consider the various
methods of standardisation which have been employed heretofore, it will be
necessary to glance for a moment at the nature and constitution of the vaccines
which are in common use.

      An anti-typhoid vaccine may be prepared in any of the following ways:—

      (a) Sterilising by heat or by some antiseptic, such as lysol or carbolic acid,
a well-grown broth culture of bacillus typhosus. This method has been
greatly used by Wright and is, we believe, the method still employed by him. A
vaccine of this nature was employed by Leishman, Harrison, Smallman and
Tulloch in a recent research¹ on the blood changes following anti-typhoid
inoculation. We shall call this 'broth vaccine'.

      Vaccines prepared by this method consist of:—

           (1) Constituents of the broth, such as peptone, etc.

           (2) The extra-cellular toxins of the bacteria.

           (3) The free "receptors" arising either by disassociation from, or by the
                 dissolution of, the bodies of the bacteria.

           (4) The undissolved bodies of dead bacteria with their infra-cellular
                 toxins and constituent receptors.

      (b) Suspending the surface growth of agar cultures of bacillus typhosus
in a fluid medium, such as normal salt solution, and then killing the bacteria in
the same way as in the case of broth cultures.

B