CADAVERIC RIGIDITY. cxxxi 



irritability even later than this, if it be struck a smart blow with a blunt edge, such as 

 the back of a knife, across the direction of the fibres. The contraction then produced 

 is quite local, and confined to the parts struck. Funke states that he and the brothers 

 Weber obtained this result in the body of a decapitated criminal twenty -four hours 

 after death. 



The time of duration is affected by the mode of death. Thus the irritability is said 

 to be almost wholly and immediately extinguished by a fatal stroke of lightning, and 

 to disappear very speedily in the bodies of persons stifled by noxious vapours, such as 

 carbonic acid, and especially sulphuretted hydrogen. In like manner certain causes 

 acting locally on muscles accelerate the extinction of their irritability. 



Rigor mortis. The " cadaveric rigidity," or stiffness of the body, which ensues 

 shortly after death, is a phenomenon depending on the muscles, which become fixed 

 or set in a rigid state, so as to resist flexion of the joints. The rigidity almost in- 

 variably begins in the muscles of the lower jaw and neck, then invades those of the 

 trunk, and afterwards those of the limbs, the arms usually before the legs. After 

 persisting for a time, it goes off in the same order. It usually comes on within a 

 few hours after death, rarely later than seven hours. In some cases it has been ob- 

 served to begin within ten minutes (Sommei'), and in others not till sixteen or 

 eighteen hours ; and the later its access, the longer is its endurance. The rigidity 

 comes on latest, attains its greatest intensity, and lasts longest in the bodies of ro- 

 bust persons, cut off by a rapidly fatal disease, or suddenly perishing by a violent 

 death ; in such cases it may last six or seven days. On the other hand, it sets in 

 speedily, is comparatively feeble, and soon goes off in cases where the body has been 

 much weakened and emaciated by lingering or exhausting diseases ; also in new- 

 born infants, and in the muscles of animals that have been hunted to death. It seems 

 thus to be affected bj the previous state of nutrition of the muscles. Destruction of 

 the nervous centres does not prevent the occurrence of rigidity, nor are the muscles 

 of paralysed limbs exempted from it, provided their nutrition has not been too deeply 

 affected. The fibres of stiffened muscles are less translucent than before, but no other 

 change is discovered by the microscope. They no longer show the muscular electric 

 current. 



The immediate cause of the muscular rigidity is doubtful : some conceive it to be 

 an effect of vital contraction, the last effort of life as it were; others, with more 

 probability, ascribe it to a solidification of the tissue caused by chemical changes 

 occurring after death. Kiihne adduces various arguments, some of them, it must be 

 admitted, of a cogent character, to show that the stiffening is due to post-mortem 

 coagulation of the myosine. He thinks that the substance of the fibre is liquid dur- 

 ing life ; but it is difficult to reconcile his notion of actual fluidity of substance with 

 some of the most obvious properties of a living muscle. At the same time, it is con- 

 ceivable that liquid myosin may be present in the interstices of more consistent 

 elements of the living fibre, and may give rise to rigidity by coagulating after death. 

 Free lactic acid is developed in the substance of rigid muscle, and some regard it as 

 the cause of the coagulation of the myosin, but although an acid condition very gene- 

 rally accompanies rigidity, the concurrence is not invariable or essential. Dr. Brown- 

 Se"quard, in opposition to the chemical theory, maintained that he could remove 

 rigidity by injecting blood into the vessels of the muscle; but Kiihne holds this to be 

 impossible after rigor has decidedly set in. The general accession of rigidity is an 

 unequivocal sign of death.* 



NERVOUS SYSTEM. 



OF the functions performed through the agency of the nervous system, 

 some are entirely corporeal, whilst others involve phenomena of a mental or 

 psychical nature. In the latter and higher class of such functions are first 

 to be reckoned those purely intellectual operations, carried on through the 

 instrumentality of the brain, which do not immediately arise from an exter- 



* The subject of muscular contraction and other questions relating to the functional 

 activity of muscle, treated of in former editions of this work, have outgrown the 

 space that could be allotted to their consideration here; and as, moreover, they properly 

 belong to a treatise on physiology, they have now been omitted. 



