THE CHEMISTRY OF MUSCLE. 125 



liquid, known as the muscle-plasma, contains myosinogen and 

 like blood-plasma is spontaneously coagulable. It quickly 

 sets into a transparent jelly and this soon separates into mus- 

 cle-serum and muscle-clot, the latter consisting of myosin. 

 Dissolved in the muscle-serum are found small quantities of 

 several albumens, one much resembling the serum-albumen of 

 blood. The spontaneous clothing of the plasma, and presum- 

 ably the natural formation of myosin during rigor mortis, are 

 due to the action on myosinogen of an enzyme, muscle-fer- 

 ment, much resembling fibrin-ferment. The clotting is 

 accompanied by a change of reaction from the alkaline or 

 neutral of the plasma to a markedly acid one: this appears to 

 be mainly due to the formation of sarcolactic acid, the quan- 

 tity of which bears a proportion to that of the myosin formed, 

 suggesting that both may be products of the breaking-down 

 of a pre-existent more complex substance. It has further been 

 shown that when a muscle passes into the state of rigor it 

 evolves a certain amount of carbon dioxide, and that the 

 quantity of this varies with the quantity of myosin and of 

 sarcolactic acid formed. Hence it has been suggested that in 

 the living muscle there is a substance which after death 

 breaks up yielding (with possibly other things) myosinogen, 

 sarcolactic acid and carbon dioxide; and further that this 

 chemical change is associated with the liberation of energy 

 (Chap. XX) which in the dead muscle is set free mainly as 

 the heat which is known to be evolved by muscles passing 

 into rigor. 



The precipitate produced when myosin solutions are 

 heated is coagulated proteid (p. 10) and insoluble in dilute 

 acids and alkalies in which myosin itself is very soluble. 

 When dissolved in dilute acids myosin is converted into syn- 

 tonin, which was formerly supposed to be the chief form of 

 proteid present in dead muscles. Syntonin is insoluble in 

 water and neutral saline solutions, but soluble in dilute acids 

 and alkalies, and its solutions are not coagulated by boiling. 



Beef Tea and Liebig's Extract. From the above-stated 

 facts it is clear that when a muscle is boiled in water its myo- 

 sin is coagulated and left behind in the meat : even if cook- 

 ing be commenced by soaking in cold water the myosin still 

 remains, as it is as insoluble in cold water as in hot. Beef tea 

 as ordinarily made, then, contains little but the flavoring 

 matters and salts of the meat, traces of some albumens and 



