THE PRODUCTION OF ENERGY IN MUSCLE 93 



The Chemistry of Rigor Caloris. — It has previously been shown 

 that the continued appUcation of heat causes the muscle to lose its 

 irritability and to become functionally useless. In this condition of 

 rigor caloris the muscle presents an opaque appearance, a firm con- 

 sistency and a change in its form, approaching its state of maximal 

 shortening. The skeletal muscles of the frog enter this condition at 40° 

 or 41° C, while those of warm-blooded animals require a temperature 

 of about 47° C. This difference in their behavior may be ascribed to 

 the fact that the muscles of amphibia contain preformed soluble 

 myogen fibrin which coagulates at 40° C, while those of mammals con- 

 tain soluble myosin which coagulates at 47° to 50° C. While rigor 

 caloris may be said to be dependent upon a conversion of the proteins^ 

 into their insoluble forms, a muscle entering this condition also liber- 

 ates carbon dioxid and heat, and acquires a larger store of lactic 

 acid. Fletcher claims that this carbon dioxid is preexisting and is set 

 free at 40° C. from carbonates and similar bodies through the inter- 

 vention of the lactic acid. At higher temperatures (75° C.) it is given 

 off by the colloids and amino-acids. 



Muscles may also be thrown into a state of rigor by means of a 

 number of chemical substances. Water-rigor, for example, results in 

 consequence of their immersion in distilled water, while coagulation- 

 rigor is the outcome of the coagulation of their protein material 

 by such agents as alcohol and chloroform. ^ The same result may be 

 obtained with dilute acids, veratrin, caffein, quinine and different tox- 

 ins.^ While it is often difficult to differentiate between these different 

 types of rigor, heat rigor mayeasily be distinguished from death rigor, 

 because the former is a permanent and the latter a temporary condi- 

 tion. Furthermore, a muscle in rigor caloris shows a more decided 

 opacity, and possesses a more solid consistency than a muscle in rigor 

 mortis. The latter is rather unevenly turbid and its color may be 

 considerably lightened by a 0.2 per cent, solution of sulphuric acid. 



CHAPTER X 

 THE PRODUCTION OF ENERGY IN MUSCLE 



Forms of Energy Liberated. — ^Life manifests itself by incessant 

 changes and every manifestation of it necessitates the Hberation of 

 energy in some form or other. Work must be done and a body that 

 cannot yield energy, accomplishes neither changes nor work. But 

 since the law of the conservation of energy applies equally to all living 

 entities, these alterations cannot be associated with a gain or loss in 



^ V. Ftirth, loc. ciL; Inagaki, Zeitschr. flir Biol, xlviii, 1907, 313, and Meiggs, 

 Am. Jour, of Physiol., xxiv, 1909, 178. 



* Brooks, Am. Jour, of Physiol., xvii, 1906, 218. 



' Heinz, Handb. der exp. Path, und Pharm., i, 1905, 576. 



