The heat produced in contracture and muscular tone

IN some experiments on the efficiency of a muscle as a machine it was noticed that the heat set free by a stimulus was not always produced at one moment but might be evolved continuously during a considerable period. Apparently under some conditions a stimulus. does not cause only an explosive, discharge of energy into heat, but also a continuous breakdown for some seconds following. It was found in allthe cases where this occurred that the muscle showed, after stimulation, that particular form of tone named " contracture ": in other words it did not reach its original -length for some considerable time after the primary twitch. It might perhaps have been expected that this was due simply to.the viscosity of the muscle, which prevented it from relaxing at once after contraction. That this contracture is always accompanied by a continuous heat production makes it probable however that it is very closely allied to the normal state of contraction. The objects of this paper are, (i) to show that contracture is accompanied by a steady heat production, and to investigate the relations between the two as far as possible, and (ii) to consider the amount of heat production during muscular tone, especially in muscles during incomplete tetanus and in the heart. Method. Blixl has described an apparatus designed by himself for estimating the heat production of working muscles. Prof. Langley some years ago obtained from him one of these instruments, with which the present investigation has been carried out. Various modifications have been applied to it, and it has been made much more sensitive and less easily disturbed than in its original form. Some idea of its sensitivity may be obtained from the statement that it is easily possible,