468 STAGES OF CADAVERIC RIGIDITY. 



further decompositions and an alkaline reaction, become soft, and the rigidity dis- 

 appears (Nysten). The onset of the rigidity is always preceded by a loss of nervous 

 activity. Hence, the muscles of the head and neck are lirst affected, and the other 

 muscles in a descending series ( 352). Disappearance of the rigidity occurs first in 

 the muscles first affected (Nysten). Great muscular activity before death (e.g., spasms 

 of tetanus, cholera, strychnin, or opium poisoning) causes rapid and intense rigidity; 

 hence, the heart becomes rigid relatively rapidly, and strongly. Hunted animals 

 may become affected within a few minutes after death. Usually the rigidity lasts 

 longer the later it occurs. Rigidity does not occur in a fcetus before the seventh 

 month. A frog's muscle cooled to C. does not begin to exhibit cadaveric 

 rigidity for four to seven days. 



Stensons Experiment. The amount of blood in a muscle has a marked effect 

 upon the onset of the rigidity. Ligature of the muscular arteries causes at first in 

 all mammals an increase of the muscular excitability, and then a rapid fall of the 

 excitability (Schmuleivitsch) ; thereafter stiffness occurs, the one stage following 

 closely upon the other (Swammerdam, Nic. Stenson, 1667). [If the ligature be 

 removed in the first stage, the muscle recovers, but in the later stages the rigidity 

 is permanent.] If the artery going to a muscle be ligatured, Stannius observed 

 that the excitability of the motor nerves disappeared after an hour, that of the 

 muscular substance after four to five hours, and then cadaveric rigidity set in. 



Pathological. When the blood-vessels of a muscle are occluded, by coagulation taking 

 place within them, rigidity of the muscles is produced ( 102). True cadaveric rigidity may be 

 produced by too tight bandaging ; the muscles are paralysed, rigid, and break up into flakes, 

 while the contents of the fibre are afterwards absorbed (B. Volkmann). Occlusion of the blood- 

 vessels of muscles by infarcts, especially in persons with atheromatous arteries, may even cause 

 necrosis of the muscles implicated (Finch, Girandeau). 



If the circulation be re-established during the first stage of the rigidity, the 

 muscle soon recovers its excitability (Stannius). When the second stage has set 

 in, restitution is impossible (Kiihne). In cold-blooded animals, cadaveric rigidity 

 does not occur for several days after ligaturing the blood-vessels. Brown-Sequard, 

 by injecting fresh oxygenated blood into the blood-vessels, succeeded in restoring the 

 excitability of the muscles of a human cadaver four hours after death, i.e., during 

 the first stage of cadaveric rigidity. Ludwig and Al. Schmidt found that the onset 

 of cadaveric rigidity was greatly retarded in excised muscles, when arterial blood 

 was passed through their blood-vessels. Blood deprived of its O did not produce 

 this effect. Cadaveric rigidity occurs relatively early after severe haemorrhage. If 

 a weak alkaline fluid be perfused through the blood-vessels of the dead muscles 

 of a frog, cadaveric rigidity is prevented (Schipilof). 



Section of Nerves. Preliminary section of the motor nerves causes a later 

 onset of the rigidity in the corresponding muscles (Brown-Sequard, Heineke). [The 

 same result occurs after a hemi-section of the spinal cord or after removal of one 

 cerebral hemisphere (Bierfreund).'] In fishes, whose medulla oblongata is suddenly 

 destroyed, cadaveric rigidity occurs much more slowly than in those animals that 

 die slowly (Rhine). 



[Other Influences. Rigidity begins much later in the red (11 to 15 hours) than in pale muscles 

 (1 to 3 hours post-mortem) ; the rigor is complete in the white muscles in 10 to 14 hours, in 

 the red in 52 to 58 hours. The extent of shortening due to the rigor is 2 to 1\ times as great 

 as iu the white. In both muscles the resolution of the rigor begins 12 to 15 hours after the 

 completion of the rigidity, so that the red muscles are not completely rigid before the other 

 muscles appear to have passed from a state of rigidity. Temperature has a marked effect, but it 

 acts more on the resolution than on the onset of the rigor. At 60 C. the onset begins almost 

 at once, and is complete in a few minutes {Bierfreund). Ether and chloroform injected into the 

 blood-vessels cause almost instantaneous rigor (Kussmaul).] 



Rigidity may be produced artificially by various reagents : 

 1. Heat [" Heat-stifFening "] causes the myosin to coagulate at 40 C. in cold- 

 blooded animals, in birds about 53 C, and in mammals at 48 to 50 C. The 



