SUMMARY: 1. Slime mold protoplasm was treated with the following anesthetic agents: carbon dioxide, cyclopropane, nitrous oxide, ethylene, ether, chloroform, and acetone.
2. Cessation of protoplasmic flow served as an indication of anesthesia.
3. That suspended animation brought on by anesthetic agents involves loss of irritability is difficult of proof in the case of slime mold protoplasm, but was shown to be true for carbon dioxide in the case of the excised chick heart.
4. Perfect anesthesia was produced by carbon dioxide, cyclopropane, and chloroform; fair anesthesia by acetone; very poor anesthesia by ether; ethylene and nitrous oxide caused no anesthetic effect whatever.
5. Cessation of protoplasmic movement was sudden when produced by carbon dioxide, cyclopropane, and chloroform.
6. The sudden cessation of protoplasmic movement produced by carbon dioxide, cyclopropane, and chloroform is due to a thixotropic setting, or rapid gelatinization, of the protoplasm.
7. Thixotropie setting is to be distinguished from gelatinization, coagulation, and increase in viscosity by its ready reversibility and the remarkable rapidity with which it takes place.
8. That slime mold protoplasm anesthetized by carbon dioxide, cyclopropane, and chloroform has set to a firm jelly whereas that treated with ether has not, is shown by applying pressure equivalent to 26 cm. of water; such a pressure readily moves protoplasm under ether, whereas carbon dioxide anesthetized protoplasm cannot be so moved.
9. Thixotropic setting is regarded as the physical change responsible for anesthesia produced by carbon dioxide, cyclopropane, and chloroform because physiological activities, including irritability, are reduced to a minimum in gelatinized protoplasm.
10. The thixotropic setting of protoplasm is due to a rapid and readily reversal locking of linear protein molecules.
(C) 1941 American Society of Anesthesiologists, Inc.