MOVEMENTS VOICE AND SPEECH. 



ing a tight ligature around the body in the lumbar region, involving all the 

 parts except the lumbar nerves. If the poison be now introduced beneath 

 the skin above the ligature, only the anterior parts are affected, because the 

 vascular communication with the posterior extremities is cut off. If the 

 exposed nerves be now stimulated, the muscles of the legs are thrown into 

 contraction, showing that the nervous excitability remains. Reflex move- 

 ments in the posterior extremities may also be produced by irritation of the 

 parts above the ligature. These experiments leave no doubt of the existence 

 of an inherent and independent excitability in the muscular tissue (Bernard). 

 Contractions of muscles, it is true, are normally excited through the nervous 

 system, and artificial stimulation of a motor nerve is the most efficient method 

 of producing the simultaneous action of all the fibres of a muscle or of a set 

 of muscles ; but electric, mechanical, or chemical irritation of the muscles 

 themselves will produce contraction, after the nervous excitability has been 

 abolished. The conditions under which muscular contractility exists are 

 simply those of normal nutrition of the muscular tissue. When the muscles 

 have become profoundly affected in their nutrition, as the result of section 

 of the mixed nerves or after prolonged paralysis, their excitability disappears 

 and can not be restored. 



Experiments have been made with regard to the influence of the cir 

 dilation upon muscular excitability, chiefly with reference to the effects 

 tying large vessels. Longet tied the abdominal aorta in five dogs and found 

 that voluntary motion ceased in about a quarter of an hour, and that the 

 muscular excitability was extinct in two hours and a quarter. When the 

 circulation was restored, after three or four hours, by removing the ligature, 

 the excitability, and finally voluntary movement, returned. These experiments 

 show that the circulation of the blood is necessary to the contractility of the 

 muscles. Tying the vena cava did not affect the excitability of the muscles. 

 In dogs in which this experiment was performed, the lower extremities pre- 

 served their contractility, and the voluntary movements were unaffected up 

 to the time of death, which took place in twenty-six hours. 



The relations of muscular excitability to the circulation have been farther 

 illustrated in the following experiments b} 7 Brown-Sequard : The first ob- 

 servations were made upon two men executed by decapitation. Thirteen 

 hours and ten minutes after death, when the muscular excitability had disap- 

 peared and was succeeded by cadaveric rigidity, a quantity of fresh, defibri- 

 nated venous blood from the human subject was injected into the arteries of 

 one hand and was returned by the veins. It was afterward re-injected sev- 

 eral times during a period of thirty-five minutes. The whole time occupied 

 in the different injections was ten to fifteen minutes. Ten minutes after the 

 last injection, and about fourteen hours after death, the excitability was found 

 to have returned in a marked degree in twelve muscles of the hand. There 

 were only two muscles out of the nineteen, in which the excitability could not 

 be demonstrated. Three hours after, the excitability still existed, but it disap- 

 peared a quarter of an hour later. The second observation was essentially 

 the same, except that defibrinated blood from the dog was used and the ex- 





