MUSCULAR CONTRACTILITY. 463 



muscular tissue. We have already seen that a muscle de- 

 tached from the living body continues for a time to respire, 

 and probably undergoes some of the changes of disassimila- 

 tion observed in the organism. So long as these changes are 

 restricted to the limits of physical and chemical integrity of 

 the fibre, contractility remains. As these processes are very 

 slow in the cold-blooded animals, the irritability of all the 

 parts persists for a considerable time after death. We have 

 repeatedly demonstrated muscular contractility, several days 

 after death, in alligators and turtles. 



In the human subject and the warm-blooded animals, the 

 muscles cease to respond to excitation a few hours after 

 death, though the time of disappearance of irritability is 

 very variable. Xysten, in a number of experiments upon 

 the disappearance of contractility in the human subject after 

 decapitation, found that different parts lost their con- 

 tractility at different periods, but that generally this de- 

 pended upon exposure to the air. With the exception of 

 the right auricle of the heart, the muscles of the voluntary 

 system were the last to lose their irritability. In one in- 

 stance, certain of the voluntary muscles that had not been 

 exposed retained their contractility seven hours and fifty 

 minutes after death. 1 The observations of Longet and Mas- 

 son show that a galvanic shock, sufficiently powerful to pro- 

 duce death, instantly destroys the irritability of the mus- 

 cular tissue and of the motor nerves. 2 



One of the most important questions to determine with 

 regard to muscular irritability is whether it be a property 

 inherent in the muscular tissue or derived from the nervous 

 system. The fact that muscles can be excited to more pow- 

 erful and regular contractions by stimulating the motor 

 nerves than by operating directly upon their substance and 

 the great difficulty in tracing the nerves to their termination 



1 XYSTEX, De la cotitractitite des organes musculaires. Eecherches de physiologie 

 et de chimie pathologiques, Paris, 1811, p. 306, et seg. 



2 LOXGET, Tratte. de physiologie, Paris, 1869, tome ii., p. 602. 



