Changes in length and ‘extension’ during the onset of rigor mortis in cyclically loaded strips of ox sternomandibularis muscle were found to be markedly different at 1 °C from those at temperatures over the range 537°C. The delay phase of rigor mortis was longer with lower temperature within the range 1.537°C, but was shorter with lower temperature within the range 1.15°C. The onset phase was longer with lower temperature within the range 5–37°, but was shorter at 1° than at 5°C.
The change in extension was completed sooner at l° than at 5° or 15°C. At 37°C, by the time the change in extension was complete, acid-labile phosphorus had fallen to a low level, and the ultimate pH was closely approached or reached; but at 1°C, an appreciable amount of acid-labile phosphorus still remained, and the pH was considerably above the ultimate value. The shortening at 1 °C was compared to thaw contracture.