THE DEATH TEMPERATURE OF NERVE

1. The irritability of frog's nerves was tested by the application of weak induction shocks, and mechanical excitation to muscle‐nerve preparations. 2. When the temperature of the Ringer's solution, in which parts of these nerves are immersed, is raised, the heated portion of the nerve loses both its excitability and conductivity at the same temperature and at the same moment. 3. This temperature is identical with that at which the first protein in the series contained within nerve‐protoplasm enters into the condition of a heat‐coagulum. 4. If the heating takes place fairly rapidly (that is, if the nerve reaches and remains at the desired temperature for a few minutes), the death temperature is 40°–41° C. 5. But more prolonged exposure to temperatures a few degrees below this effects the same result. The lowest temperature used (36·50°C.) accomplishes this end in a little over an hour. 6. This is exactly parallel to what happens when one heats the protein extracted from nervous tissue by saline solution. Opalescence, the initial visible sign of heat‐coagulation, sets in at 36°C., and if the heating is prolonged at this temperature culminates in the production of flocculi. 7. It is also paralleled in experiments on the shortening of nerve under the influence of heat; shortening begins at the temperature of opalescence, and although it is not energetic until 40°C. is reached, full shortening can be obtained at the lower temperature provided sufficient time is allowed. 8. The abolition of nervous irritability produced by such temperatures is like the heat‐coagulation of a protein in being an irreversible phenomenon. 9. Alcock's conclusion that the cause of ilerve‐death at an elevated temperature is due to the coagulation of the first protein is thus fully confirmed. 10. This is strengthened by the consideration that in warm‐blooded animals the death temperature of nerve is higher, and is there again identical with the coagulation temperature of the first of the series of proteins contained in this variety of nerve. 11. Alcock's method was different from the one mainly used in the present research. He employed the galvanometric response as the “sign of life” in the nerves he used, and heated his nerves for periods of 5 minutes. 12. I have, however, in a few experiments used this method also, and find that a temperature as low as 36·5°C. will abolish the electrical sign of life, provided it has been kept up for a little more than an hour. 13. v. Miram's results in which he puts the death temperature of frogs' nerves at 47°C., I am wholly unable to explain. I am indebted to the Government Grant Committee of the Royal Society for a grant which has enabled me to pay the expenses of this investigation. A few years ago I placed the research in the hands of my former demonstrator, Mr V. W. Draper, B.Sc., but, after a few preliminary experiments which I have incorporated in the present paper, he was obliged to abandon the work owing to ill‐health.