NERVOUS SYSTEM. Ur, 



In like manner certain causes acting locally on muscles accelerate the extinction 

 of their imtability. 



Bigor 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 invariably 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 observed to begin within ten minutes (Sommer), 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 robust persons, cut off by a rapidly fatal disease, or sud- 

 denly 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-bom infants, and in the muscles of animals 

 that have been hunted to death. It seems thus to be affected by the previous 

 state of nutrition of the muscles. Destruction of the nervous centres does not 

 jjrevent the occurrence of •x'igidity, nor are the muscles of paralysed limbs 

 exempted from it, provided their nutrition has not been too deeply affected. The 

 fibres of stiffened muscles 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 coagnilation of the myosin. He thinks that the substance of the 

 filire is liquid diu-ing life ; but it is difficult to reconcile liis notion of actual 

 fluidity of substance Avith some of the most obvious properties of a living muscle. 

 At the same time, it is conceivable that liquid myosin 'may be present in the 

 interstices of more consistent elements of the living fibre, and may give rise to 

 rigidity by coag-ulating after death. Free lactic acid is developed in the sub- 

 stance of rigid nniscle, and some regard it as the cause of the coagulation of the 

 myosin, but although an acid condition very generally accompanies rigidity, the 

 concurrence is not invariable or essential, Bro'^m-Sequard, in opposition to the 

 chemical theory, maintained that he could remove rigidity by injecting blood 

 into the vessels of the muscle ; but Kllhne holds this to be imi^ossible after rigor 

 has decidedly set in. The general accession of rigidity is an unequivocal sign of 

 death. 



nSTEKVOUS SYSTEM. 



The nervous system consists of a central jKirt, or rather a series of 

 connected central organs, named the ccrehro-spinal axis, or cerchro-spinal 

 centre; and of the ;?f/7r.<f, Avhich have the form of cords connected by 

 one extremity with the cerebro-spinal centre, and extending from 

 thence through the body to the muscles, sensible parts, and other organs 

 placed under their control. The nerves form the medium of communi- 

 cation betv^^een these distant parts and the centre. One class of nervous 

 fibres, termed ctfferent or centripetal, conduct impressions towards the 

 centre, — another, the efferent or centrifugal, carry motorial stimuli from 

 the centre to the moving organs. 



Besides the cerebro-spinal centre and the nervous cords, the nervous 

 system comprehends also certain bodies named ganglia, which are con- 

 nected with the nerves in various situations. These bodies, though of 

 much smaller size and less complex nature than the bram, agree, never- 



