DEA TH OF MUSCLE. 391 



from going into rigor, by subjecting it immediately after removal to a tempera- 

 ture approaching 0' C, and that a liquid squeezed out of it by pressure when in this 

 state, remains fluid so long as this temperature is maintained, but that myosin 

 separates from it as soon as the temperature rises ; and, further, that although 

 a certain quantity of liquid can be squeezed out of muscle which not having 

 been kept cold had become rigid, this is incapable of spontaneous coagulation, 

 inasmuch as it contains no myosin. It thus appeared as if the characteristic 

 proteid of muscle were affected by low temperature in the same way as the 

 muscular tissue itself, and this seemed to afford a cogent proof that in the pro- 

 perties of myosin the explanation of rigor was to be found. There were, how- 

 ever, always those who held to the old view of Nysten, that in muscle the 

 process of death is continuous with that of life. Brown-Sequard indicated as 

 the result of numerous observations, partly clinical, partly experimental, that 

 rigor occurs under conditions which can have nothing to do with coagulation, 

 that it occurs in muscles which are still " living," that it associates itself with 

 excitatory states, and that it can be warded off by passive movement, recurring 

 when this is discontinued. Schiff 1 also found it to be closely related to 

 certain forms of contraction, particularly that localised form to which he 

 applied the term " idiomuscular." 



The true relation of the spasmodic to the other phenomena of 

 rigor was not ascertained with accuracy until in 1881 the inquiry was 

 taken up by Hermann and worked out by his pupils. By them it was 

 shown, both in the frog and in mammals, that rigor was retarded in the 

 muscles of a limb by severing its nerves, or by hemisection of the spinal 

 cord, the operation being in either case performed immediately after death, 

 so as to avoid the possibility of interference with the previous state of the 

 circulation or nutrition of the muscles. It thus appeared that the nervous 

 system continues to exercise a certain influence on the muscles after 

 death, and that interference with the innervation of a muscle is un- 

 favourable to the development of rigor. The following experiment of 

 Nagel 2 makes it probable that this statement may be extended to the 

 peripheral parts of motor nerves : — 



A frog, in which one hind-limb has been protected by ligature, is curarised ; 

 the spinal cord is destroyed, and both sciatics are immediately divided. It is 

 then found that rigor is retarded on the curarised side as compared with the other 

 side, a result which shows that, even when separated from the central nervous 

 system, the peripheral parts of the motor nerves exercise an influence in initiat- 

 ing the post-mortem contraction of the muscles to which they are distributed. 



From the observations of Bierfreund, 3 it appears that muscles which con- 

 tract differently also behave differently with regard to rigor. Thus, in the 

 red muscles of the rabbit the post-mortem contraction is so much retarded as 

 compared with that of the pale muscles, that the contraction of the latter may 

 have ceased at the time that that of the other is only half over (Fig. 217). 



Other differences in the behaviour of muscles in rigor, depending upon 

 individual peculiarities of the muscles themselves, have been observed by 

 Langendorff and Gerlach. 4 When the hind-limbs of a frog are freely sus- 

 pended in normal salt solution, the attitudes which they assume indicate that 

 the flexors pass into rigor before the extensors. Nagel has confirmed this 

 observation as regards toads and certain specimens of R. temporaria which had 

 been kept through the winter. In other frogs he found that both sets of 

 muscles went into rigor simultaneously. 



1 1858, In "Beitr. z. Physiol.," 1894, Bd. ii. S. 9, 18. 



- Arch. f. d. ges. Physiol., Bonn, Bd. lviii. S. 279. 



* Ibid., 1888, Bd. xliii. S. 195. 4 Ibid., Bd. lviii. S. 279-308. 



