UNUSUAL CASE OF CHRONIC RINDERPEST.                    359

have expressed the same opinion a reference to Littlewood [ 1905 ] of Egypt will
be made later in this paper.

                                 TENACITY OF THE VIRUS.

Very conflicting results have been recorded by different workers with regard
to the tenacity of the rinderpest virus in blood when kept in vitro and yet it is a
question that cannot be left in this unsatisfactory state in view of the practical
application such information has in the serum-simultaneous method of inoculation.
Even prior to the achievement of Nicolle and Adil Bey [ 1902 ] in establishing the
filterability of the causal agent, Koch [ 1897 ] found that the virulence of rinderpest
blood is destroyed by prolonged exposure (of 4 hours) to a temperature of 30° C.,
and that blood so treated produced no " protective action " on being injected into
cattle. On the other hand, Theiler [ 1898 ] found that blood when subjected to a
higher temperature of 37° C. for 2 or 3 days became avirulent. In testing the
practical applicability of the serum-simultaneous method of inoculation, Stockman
[ 1905 ] experienced difficulty in maintaining blood from a sick ox virulent for more
than 48 hours even when kept in the ice chest under field conditions in both India
and South Africa. Again Todd & White [ 1914 ] claimed that virulent blood taken
in citrate solution and kept in sealed tubes at —6° to —7° C. retained its virulence up
to 22 weeks. Results indicating the retention of virulence by rinderpest blood for
prolonged periods such as the above have been obtained by Shilston [1917]. Al-
though the virus in blood, meat and bone marrow was found to survive at air
temperature ordinarily from 2 to 9 days, he quotes instances from his experience in
which blood stored under aseptic conditions at room temperature remained virulent
for periods of 30-40 days and in one instance up to 51 days. Further in another
case blood at 0° C. was virulent even after 90 days. Recently Malanidi and
Stylianopoulo [ 1927 ] found that 2 c.c. of blood kept in cold store for nine days
produced a mild thermal reaction only in a calf.

Leaving aside reports of prolonged viability of the virus under artificial
conditions, our ideas in regard to the conservation of the virus in blood at ordinary
air temperature for 51 days would appear to require revision, as will be noticed
from the later findings of Edwards [1924] who states :—

       " Experiments with virluent blood stored at body temperature, however,
              showed that the infective agent became inert usually within three days
              when it was exposed to air, but that it survived very considerably
              longer, ten days or more, when it was covered with a seal of liquid
              paraffin. The factor of greatest importance appeared to be the trans-
              formation that took place in the blood owing to the escape of carbon
              dioxide gas and destruction of the virus was rapid during this transforma-
              tion ".