148 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



the coagulation of muscle-plasma and myosin solutions. He called the sub- 

 stance thus obtained myosin ferment. The extract obtained contained an 

 albumose which was either the ferment or held it in close combination. The 

 pure ferment has not been isolated. The myosin ferment is not the same as 

 fibrin ferment, since neither can do the work of the other. Moreover, fibrin 

 ferment is destroyed at 75-80 C. and myosin ferment is not destroyed till 

 100 C. 



In several respects there is a close resemblance between the behavior of 

 blood- and muscle-plasma, but the coagulated products differ. Kuehne found 

 that myosin could be dissolved by a dilute saline solution, and that, on further 

 dilution, it was reprecipitated. Halliburton observed that a saline solution of 

 myosin, diluted twenty times with water, gave a precipitate which could be 

 dissolved in a 5 per cent, magnesium-sulphate solution, and then by the addi- 

 tion of water be made to recoagulate. In these respects myosin differs markedly 

 from fibrin. Fibrin is dissolved only with difficulty in dilute saline solutions 

 and cannot be recoagulated. Myosin also differs from fibrin by its greater 

 solubility in dilute HCl. 



Moreover, the chemical change which results in the formation of myosin is 

 different from that which produces fibrin. The clotting of muscle-plasma and 

 the formation of myosin is accompanied or closely followed by the production 

 of an acid, while no such change occurs during the coagulation of blood-plasma. 

 In the earlier stages of clotting the acidity may be due in part to acid potassium 

 phosphate, but the final acidity is chiefly due to lactic acid. The source of the 

 lactic acid has not been definitely made out. The view that it comes from 

 glycogen is made questionable by Boehm's 1 observation that the amount of 

 glycogen is not lessened in rigor, and is corroborated by the observation that 

 the muscles of starving animals become acid when entering into rigor, although, 

 as Bernard found, they contain no glycogen. Boehme concluded that the 

 sarcolactic acid is formed from the proteids, and this is accepted by other good 

 observers. 



Some writers have thought the coagulation of the muscle was the result of 

 the formation of an acid by the dying muscle. This is unlikely, although the 

 presence of acid, like that of many other substances, quinine, caffein, digitalin, 

 veratrin, hydrocyanic acid, ether, chloroform, etc., 2 may hasten the process. 

 This may account for the rapidity with which rigor comes on in fatigued 

 muscles. 



2. Constituents of Muscle-serum and. Changes resulting from Con- 

 traction. Muscle-serum can be most readily obtained by mincing a muscle 

 in rigor mortis and expressing the fluid. The proteids of the serum can be 

 separated by the degrees at which they undergo heat-coagulation. 



The method of fractional heat-coagulation was employed by Halliburton 3 

 to determine the proteids of muscle. He found the following : 



1 Pfliiger'sArchiv, 1880, Bd. xxiii. 8. 44. " Halliburton : Physiological Chemistry, p. 414. 

 3 Journal of Physiology, viii. pp. 184-186. 



