368 THE MUSCLE-TISSUE. 



with acids or alkalies ; and here, as there, a precipitation results 

 only if very dilute acids are used. In an excess the precipitate 

 rapidly dissolves. On heating solutions of myosin to 35 C. the 

 substance is gradually coagulated, while this occurs at once at a tem- 

 perature of 50 C. 



In its insoluble form myosin is termed myotin-fibrin, which, like 

 the insoluble myogen-fibrin, belongs to the class of the coagulated 

 albumins. 



Of special interest, further, is the fact that on evaporating a few 

 drops of a solution of myosin in soda solution on a slide, at a low 

 temperature, a jelly-like material is obtained, which on polariscopic 

 examination is seen to be doubly refracting. In this respect it 

 behaves exactly as the anisotropic material which is found in the 

 dark bands of the voluntary muscle-fibres. 



The amount of myosin found in the muscle-tissue of the rabbit is 

 much less than that of myogen, and, according to v. Furth, corre- 

 sponds to only 20 per cent, of the total amount of soluble albumins. 



Significance of the Common Muscle -albumins. Of the part 

 which the common muscle-albumins take in the function of the cell 

 little is known that is definite. From the researches of some ob- 

 servers, it appears that the nitrogenous components of the albumins, 

 at least, do not furnish the energy which is here required. Petten- 

 kofer and Yoit have thus shown that an increase in the amount of 

 muscular work does not lead to an increased elimination of nitrogen 

 or causes an increase which is insignificant. This view is now gener- 

 ally held ; but it must be admitted that evidence is not lacking 

 which suggests that an increased albuminous destruction may occur 

 nevertheless when the amount of work is increased. It has been 

 shown, as a matter of fact, that the total elimination of sulphur, 

 which usually follows that of the nitrogen quite closely, is increased 

 by muscular exercise and diminished thereafter. But while we may 

 admit that the nitrogenous components of albumin may furnish a 

 certain fraction of the energy which is required in muscular work, 

 this is, after all, but slight, and there is abundant evidence to show 

 that by far the greater amount of energy must be referable to the 

 decomposition of non-nitrogenous material. 



The question, of course, suggests itself, Do the soluble albumins 

 of the muscle-plasma represent the contractile element of the 

 muscle-tissue? but to this question no answer can as yet be given. 

 We might imagine that in some manner a transformation of the 

 soluble albumins into the fibrin form occurs, and vice versa ; but of this 

 we have no evidence in the living tissue. On the other hand, it is 

 supposed that rigor mortis, as well as the rigor which results from 

 exposure of muscle-tissue to a temperature of 47 C., is owing 

 to such a change, and it is possible that in either event both 

 myosin and myogen pass over into the coagulated state. Folin in a 

 recent j.aper, however, has again thrown doubt on the correctness 

 of the coagulation theory in the explanation of rigor mortis, and has 



