1. Brown, F., andB. Cartwright: Purification of the virus of foot-and-mouth disease by fluorooarbon treatment and its dissociation from neutralizing antibody. J. Immunol.85, 309?313 (1960).
2. Burrows, R.: Studies on the carrier state of cattle exposed to foot-and-mouth disease virus. J. Hyg. (Lond.)64, 81?90 (1966).
3. Callis, J. J., andG. E. Cottral: Methods for containment of animal pathogens at the Plum Island Animal Disease Laboratory. In: Methods in Virology IV. (K. Maramorosch andH. Koprowski, eds.) pp. 465?480. New York: Academic Press, 1968.
4. Cunliffe, H. R.: Observations on the duration of immunity in cattle after experimental infection with foot-and-mouth disease virus. Cornell Vet.54, 501?510 (1964).
5. Curtain, C. C., B. L. Clark, andJ. H. Dufty: The origins of the immuno- globulins in the mucous secretions of cattle. Clin. exp. Immunol.8, 335?344 (1971).