12

     The practical bearings of the results of these observations are so patent as
to require no further discussion.

Protocols.

SERIES No. 1.—Experiments to determine the minimum lethal dose of pure
cobra venom for a rat of about 118 grammes.

     The poison used was carefully dried pure fresh cobra venom. It was
unheated. A 0.1 per cent. solution in sterile normal saline solution was made.
Ten-fold and hundred-fold dilutions of this original solution were used when
necessary. The weights refer to the original dried venom.

     All rats were carefully selected about 118 grammes weight. The injections
were made subcutaneously in the inner side of the thigh.

     From the above table it appears, then, that 0.04 mgrm. is a certain lethal
dose, and that 0.035 mgrm. is a dose which a rat of this size can survive, i.e.,
a maximum non-lethal dose.

     In the series of experiments No. II to No. VIII, detailed hereafter, ten lethal
doses,—namely, mgrm.—were mixed in vitro with varying amounts of sera of
different ages and which had been kept under different conditions of temperature.
The mixtures were allowed to stand at laboratory temperature (about 25° C.)
for at least half an hour, and were then injected subcutaneously in the inner