MUSCLES. 481 



animal is poisoned by opium, the actions of the involuntary muscles 

 of the heart and intestines continue after the voluntary muscles 

 have ceased to contract on the application of the scalpel k ; the 

 power continues longer in the muscles of the young than of 

 the old ; of the well fed than of the ill fed ; in warmth than in 

 cold ; in atmospheric air and oxygen than in irrespirable gases ; 

 and strong stimuli, chemical agents, or narcotics, applied to 

 either muscles or their nerves, rapidly annihilate their powers. 1 

 Repeated stimulation exhausts a muscle more slowly if its nerves 

 have been divided, because, while the nerves are in connection 

 with it ra , the stimulus affects them also and thus the muscle 

 indirectly as well as directly. If the power of contraction de- 

 pended on the nerves, the division of the nerves, by cutting off 

 the supply of power, should hasten exhaustion. Vegetables 

 have no nerves, and yet exhibit striking movements. If a 

 muscle, in a mean state of extension, is divided transversely 

 in the living body, the two portions instantly separate ; and Bi- 

 chat found that they separate just as far if its nerves have been 

 previously divided, another fact in harmony with the opinion 

 of the contractility of muscles being inherent. To ascribe mus- 

 cular excitability to the nervous system, is but an individual 

 instance of the ascription of the vital properties of all parts to 

 the nervous system, an opinion which I endeavoured to refute 

 at page 4-31. sqq. supra. n Still the contraction of voluntary 

 muscles is not only excited by nerves at the moment of volition, 

 but preserved constantly to a certain point by the encephalo- 

 spinal nerves of motion, because, if connection with them is de- 

 stroyed, or the portion of the encephalon or spinal chord with 

 which they unite is disorganised or compressed, the antagonist 

 muscles, as those of the face, overpower them, or the sphincter 

 of the rectum or bladder is no longer able to retain. Thus in 

 hemiplegia the muscles of the mouth half draw their antagonists 



k Of course galvanism to their nerves is equally inoperative. Dr. C. Henry, 

 I.e. p. 16. 



1 Dr. Tiedemann, 1. c. ccccxlv. 



m Dr. Wilson Philip, Exp. Inquiry, p. 100. 



u Whytt, in opposition to Haller, contended that the susceptibility of excite- 

 ment in muscles, the recognition of stimulus, depended altogether upon their 

 nerves ; and that stimuli excite them by producing an uneasy feeling in them or 

 their nerves. Essay on the Vital and Involuntary Motions of Animalt. Edinb. 

 1751. 



K K 2 



