THE MUSCULAK SYSTEM. 419 



with the magnetic interrupter. The rapidly succeeding shocks given by 

 this means to the nerves of muscles excite in all the transversely-striated 

 muscles, except in the case of the heart, a fixed state of tetanic contrac- 

 tion as previously described, which lasts as long as the stimulus is con- 

 tinued, and on its withdrawal instantly ceases; but in the muscles with 

 nnstriped fibres they excite a slow vermicular movement; which is com- 

 paratively slight and alternates with rest. It continues for a time after 

 the stimulus is withdrawn. 



In their mode of responding to these stimuli, all the skeletal muscles, 

 or those with transverse striae, are alike; but among those with unstriped 

 fibres there are many differences a fact which tends to confirm the 

 opinion that their peculiarity depends as well on their connection with 

 nerves and ganglia as on their own properties. The ureters and gall- 

 bladder are the parts least excited by stimuli; they do not act at all till 

 the stimulus has been long applied, and then contract feebly, and to a 

 small extent. The contractions of the caecum and stomach are quicker 

 and wider-spread: still quicker those of the iris, and of the urinary blad- 

 der if it be not too full. The actions of the small and large intestines, 

 of the vas deferens, and pregnant uterus, are yet more vivid, more regu- 

 lar, and more sustained; and they require no more stimulus than that of 

 the air to excite them. The heart, on account, doubtless, of its striated 

 muscle, is the quickest and most vigorous of all the muscles of organic 

 life in contracting upon irritation, and appears in this, as in nearly all 

 others respects, to be the connecting member of the two classes of 

 muscles. 



All the muscles retain their property of contracting under the influ- 

 ence of stimuli applied to them or to their nerves for some time after 

 death, the period being longer in cold-blooded than in warm-blooded 

 Vertebrata, and shorter in Birds than in Mammalia. It would seem as 

 if the more active the respiratory process in the living animal, the 

 shorter is the time of duration of the irritability in the muscles after 

 death: and this is confirmed by the comparison of different species in 

 the same order of Vertebrata. But the period during which this irri- 

 tability lasts, is not the same in all persons, nor in all the muscles of 

 the same persons. In a man it ceases, according to Nysten, in the fol- 

 lowing order: first in the left ventricle, then in the intestines and 

 stomach, the urinary bladder, right ventricle, oesophagus, iris; then in 

 the voluntary muscles of the trunk, lower and upper extremities; lastly, 

 in the right and left auricle of the heart. 



C. Rigor Mortis. 



After the muscles of the dead body have lost their irritability or capa- 

 bility of being excited to contraction by the application of a stimulus, 

 they spontaneously pass into a state of contraction, apparently identical 

 with that which ensues during life. It affects all the muscles of the 

 body; and, where external circumstances do not prevent it, commonly 

 fixes the limbs in that which is their natural posture of equilibrium or 

 rest. Hence, and from the simultaneous contraction of all the muscles 



