THE PROPERTIES OF RESTING MUSCLE 413 



Such a curve is given in Fig. 152. We see that the increase in length 

 of the muscle with a load increasing at a uniform rate is less, the greater 

 the absolute load i. e., the coefficient of elasticity becomes greater as the ten- 

 sion of the muscle increases. Moreover, it appears from the figure that the 

 elasticity curve runs below the extension curve, a circumstance not due to 

 after extension. The elasticity, it will be observed, is very complete, since the 

 muscle when it is released resumes its original length. Permanent lengthen- 

 ing appears to a noticeable extent only when the muscle substance is torn 

 by too great an extension. 



B. CHEMISTRY OF MUSCLE 



The reaction of fresh, resting muscle was for a long time regarded as 

 acid. But Du Bois-Reymond pointed out that the reaction of the flesh of 

 different mammals is more or less alkaline. Further investigation has shown 

 that there is no one reaction for resting muscle, but rather two: alkaline to 

 lacmoid and neutral or faintly 

 alkaline to curcuma. The 

 aqueous extract of cross- 

 striated muscle reacts in the 

 same way. According to Roh- 

 mann, the acid reaction of the 

 water extract to curcuma is 

 essentially due to sodium 

 monophosphate, and. the alka- 

 line reaction to lacmoid to the 

 acid carbonate of sodium, to 

 the diphosphate of sodium and 



to alkaline compounds of the FlG - ^.-Extension and elasticity curves of the frog's 



. i gastrocnemius, after JNerander. Ihis tracing was 



proteiQS. obtained with the apparatus shown in Fig. 151. 



The upper line represents the curve of extension and 

 Among the proteids which the lower line the curve of elastic shortening. 



make up the insoluble stroma 



of muscle, there are two bodies, one a globulin (myosin, v. Furth; paramyo- 

 sinogen, G. N. Stewart) and the other a globulin-like substance (myogen, 

 v. Fiirth; myosinogen) which can be extracted from fresh, blood-free rabbit's 

 muscle with normal salt solution. In dead muscle both pass over spontane- 

 ously into insoluble modifications (myosin fibrin and myogen fibrin) but they 

 are distinguished by their precipitation reactions and the temperature at 

 which they coagulate. Myosin coagulates at 44-50 C., myogen at 55-65 

 C. Of the total quantity of proteid which goes into solution with normal 

 salt, myosin constitutes about twenty per cent and myogen about eighty per 

 cent (v. Fiirth). 



Other nitrogenous constituents of muscle represent the decomposition prod- 

 ucts of proteid: creatin (0.1-0.4 per cent in fresh muscle), hypoxanthin, xanthin, 

 and guanin (0.23, 0.05 and 0.02 per cent of dry substance respectively). 

 Here belong also the phosphocarnic acid (0.1-0.2 per cent) ; inosinic acid 

 (C 10 H 13 N 4 PO 8 ) from which hypoxanthin can be split off; carnosin (C 9 H ]4 N 4 O 3 ) 

 closely related to arginin; and carnin (C 6 H 8 N 4 O 3 ). 



The nonnitrogenous organic constituents are: inosit (hexa-hydroxy-benzol, 

 C fl H 6 (OH 8 +H 2 O), glycogen, sugar, fat, etc. 



