392 



THE PROPERTIES OF STRIPED MUSCLE. 



As regards the cessation of rigor, Bierfreimd showed that it was neither 

 due, as Briicke supposed, to the development of acid reaction, nor, as other 

 observers have thought, to the commencement of putrefactive change, but that 

 the time of its occurrence is rather dependent on individual peculiarities of the 

 muscle used. That it is not due to sepsis, is proved by the fact that it occurs 

 in muscles perfectly sterilised by the injection of salt solution containing car- 



FIG. 217. Showing curves of rigor mortis of white (gastrocne-itiius) and red 

 (soleus) muscles of rabbit. Rigor occurs eight hours after death in the 

 former, fifteen hours in the latter. The red muscle also shortens more than 

 the pale. On comparing these curves -with the ordinary isotonic curves of 

 the same muscles, their heights are found to be in similar proportion to 

 each other. After Bierfreund. 



bolic acid. This, however, does not exclude the possibility that a putrefactive 

 change, if present, might arrest rigor ; and Nagel l has mentioned instances 

 in which the early occurrence of putrefaction was associated with the absence 

 of rigor. ISTagel, however, agrees with Bierfreund in not regarding putrefaction 

 as the ordinary cause of cessation of rigor, for he has also found many cases 

 of rigor persisting in muscles which have undergone a good deal of putre- 

 factive change, and some in which 

 it has appeared, although no putre- 

 factive change could be perceived. 



The well-known fact that a 

 muscle exhausted by previous 

 tetanisation, or by the spasms of 

 strychnine, passes more quickly 

 into rigor than a normal muscle, 

 is well illustrated by an experi- 

 ment of Xagel, of which Fig. 218 

 gives the result. The shortening 



. of a gastrocnemius, which had 

 FIG. 218. Curves of rigor mortis in fresh and , . , 



exhausted muscle.- After Nagel. been repeatedly tetanised, was 



compared with the unfatigued 



gastrocnemius in another frog. Rigor supervened sixteen hours later in the 

 one than in the other. 



It lias already been mentioned that Schiff, at an early period, con- 

 nected the incipient stage of rigor with localised or " icliomuscular " 

 contractions. He imagined that it might be initiated by the direct 

 action on the still excitable muscular substance, of some product coining 

 into existence either after death or when death was approaching. The 



1 Loc. cit., 1894, Bd. Iv. S. 481. 



