Note by A. A. Kanthack, M.A., M.D., F.R.C.P., F.R.C.S., Fellow of
King's College and Professor of Pathology in the University
of Cambridge.

      Dr. D. D. Cunningham was kind enough to send me his manuscript for
perusal, knowing that in my laboratory we were working on the same subject.
He requested me to add to his own observations. I do this all the more willingly
since I owe all the cobra poison, which I possess, to Dr. Cunningham, so that I feel
that by adding these brief notes I am acknowledging in some slight measure my
indebtedness to the late Superintendent of the Zoological Gardens of Calcutta.
The lines appended by me form an abstract of experiments executed under my
direction by Messrs. J. W. W. Stephens, John Lucas Walker Student in Pa-
thology at the University of Cambridge, and W. Myers.

      These experiments were made primarily with the object of studying the
mode of action of an antitoxin on its corresponding toxin.

      Ehrlich in 1897 showed that a toxin can react chemically upon the antitoxin
in vitro. Ricin, the toxin which he used, produces a curious effect upon
defibrinated blood, the corpuscles being firmly clumped together and precipitated.
Ehrlich filled 6 test tubes each with 95 c.c. of physiological saline solution
containing 5% citrate of sodium and added thereto 5 c. c. of rabbit's blood. 1 c.c.
of a 2% ricin solution would quickly precipitate the corpuscles. He added to 5 of
the above test tubes severally 1 c. c. of 2% ricin solution mixed respectively with
0.3, 0.5, 0.75, 1.0, and 1.25 c.c. of diluted antitoxin, while to the 6th tube he added
1 c.c. of the ricin solution without the antitoxin. The result was that the addition
of 1.25 and 1.0 c.c. of antiricin neutralized the action of the ricin in the test tube,
while 0.3 c.c, had no appreciable effect, and 0.5 merely delayed the clumping and
precipitation, whereas with 0.75 c.c. the clumping was imperfect as well as
delayed. He now proceeded to test these mixtures of ricin and antiricin upon
mice, and found that the addition of 1.25 and 10 c.c. of antiricin had neutralized
the ricin also for the animal while 0.3 c. c. had no effect, 0.5 delayed death
and 0.75 c.c. weakened its action to such an extent that nothing more than a
moderate infiltration resulted. It is evident, therefore, that the animal experi-
ments confirm the test tube experiments, and Ehrlich has thus shown that ricin
and antiricin directly influence each other chemically without the assistance
of cellular activity.

      In studying the action of cobra-toxin and its antitoxin,: therefore, a simple
reaction was sought for, which could be demonstrated outsider the body in test
tubes; and to this end, an investigation was made upon the action of cobra.
poison upon blood.