‘Sir,- Dr. Templeton, in his interesting account in the British Medical Journal of May 26th, referring to the difficulty of obtaining the Plasmodium vivax in this country, says: "Attempts are being made to keep the parasite alive outside the body; so far it has not survived more than eight hours." He does not refer to the cultivation of the parasites in vitro, but it has been cultivated in a suitable medium by several workers; and Drs. J.D. Thomson and H. P. Woodcock, writing in Byam and Archibald's Practice of Medicinie in the Tropics (II, 1542), mention that " it is considered that there is no reason why the growth and multiplication of the parasites in the culture should not continue indefinitely, provided that fresh serum and corpuscles are added to the medium when necessary." Might not this method then, give the necessary supply of the parasite for use in the treatment of general paralysis?

I am, etc.,

George A. Williamson.’