The thermal degradation of rabies virus was determined by the variation in optical density at 260 nm during temperature rise. This variation, linked to denaturation of RNA, was seen by an irreversible sigmoidal curve. Analysis of the state of the virion by ultracentrifugation did not show any alteration in sedimentation. Electron microscopy revealed a release of nucleic acid of the virions which were burst to a greater or lesser degree. The technical conditions of these measurements--speed of temperature rise and virus preparation--are defined. The form of the curve and the different measurements which develop from it, enable the influence of numerous factors linked either to the sodium, calcium and magnesium environment, or to an alteration of the virus by chemical substances, especially inactivation agents, to be observed. The study of the thermal degradation of rabies virus is an interesting method of determining the action of different factors on the stability of the virion.
Animals Cricetinae