288 OF MUSCULAR CONTRACTILITY. 



of an explanation of their effect on muscular action. It is worthy of remark, 

 that whilst the influence of general depressing causes acting through the 

 Nervous System, is primarily manifested on the muscles of Organic life, that 

 of stimulants chiefly shows itself in the muscles subjected to the will. 



389. The last general question now to be considered regarding Muscular 

 Contractility, is that which relates to the Rigor Mortis. The temporary stif- 

 fening of the body after death, from a general contraction of its muscles, is a 

 phenomenon which is rarely absent ; though it may be so slight, and may last 

 for so short a time, as to escape observation. The period which elapses before 

 its commencement, is as variable as its duration ; and both appear to be in some 

 degree dependent upon the vital condition of the body at the time of death. 

 When the fatal termination has supervened on slow and wasting disease, occa- 

 sioning great general depression of the vital powers, the rigidity usually 

 develops itself very early, and lasts for a short time. In diseases which pow- 

 erfully affect the nervous energy, such as Typhus, this is the case ; even 

 though they have not been of long duration. Thus, after death from Typhus, 

 the limbs have been sometimes known to stiffen within 15 or 20 minutest The 

 same is observed in infants and in old people. On the other hand, where the 

 general energy has been retained up to a short period before death, the rigidity 

 is much later in coming on, and lasts longer ; this happens, for example, in 

 many cases of Asphyxia and Poisoning, in which it has been said not to occur 

 at all. The commencement of the rigidity, however, is not usually prolonged 

 much beyond seven hours ; but twenty or even thirty hours may elapse before 

 it shows itself. Its general duration is from twenty-four to thirty-six hours ; 

 but it may pass off much more rapidly, or it may be prolonged through seve- 

 ral days. An attempt has been made to connect it with the lowering of the 

 temperature of the dead body ; but with this it does not seem to have any rela- 

 tion. It occurs in cold-blooded Vertebrata, and even in Invertebrata, as well 

 as in warm-blooded animals; and it has frequently been noticed to commence 

 in the latter Jong before the heat has entirely departed from the body. Moreover, 

 it appears first upon the trunk, which is the region last deserted by the caloric. 

 It first affects the neck and lower jaw, and seems gradually to travel down- 

 wards; but, according to some observers, the lower extremities are stiffened 

 before the upper. In its departure, which is immediately followed by decom- 

 position, the same order is observed. It affects all the muscles nearly alike ; 

 but the flexors are usually more contracted than the extensors, so that the 

 fingers are somewhat flexed on the palm, and the forearm on the arm; and the 

 lower jaw, if previously drooping, is commonly drawn firmly against the upper. 

 It is remarkable that it is equally intense in muscles which have been para- 

 lyzed by Hemiplegia, provided that no considerable change has taken place 

 in their nutrition. 



390. The Muscular contraction which gives rise to the Rigor Mortis, appears 

 to be of the same kind with that which takes place under the influence of 

 nervous agency, though differing as to its conditions. When very strong, it 

 renders the muscles prominent, as in voluntary contraction; and the compara- 

 tive observations of Mr. Bowman, upon the state of muscular fibre passing 

 into this condition, and upon that which presented various degrees of contrac- 

 tion from ordinary causes, leave no doubt as to their correspondence. It is to 

 be remarked, however, that the tendency of the muscle to contract upon the 

 ordinary stimuli, appears to be almost invariably lost, or greatly diminished, 

 before the rigor mortis commences. This statement holds good in regard to 

 animals of different classes, as well as with respect to Man under various con- 

 Ihus, in Birds whose muscles most speedily lose their contractility, 

 the cadaveric rigidity is most quickly exhibited; whilst in Reptiles it is much 

 longer m commencing, the irritability of the muscles being more persistent. 



