MUSCULAR MOTION. 



521 



description that though contractility remained, 

 it was diminished proportionally to the wasting, 

 in the limbs that had not been exercised. 



The results of this admirably devised experi- 

 ment cannot possibly be reconciled with the 

 opinion that the spinal cord has any necessary 

 or immediate influence in conferring contracti- 

 lity on muscles that it is the source whence 

 that property is derived. On the contrary, they 

 show in a manner that admits of no dispute 

 that both contractility and nutrition have been 

 preserved together by the continued activity of 

 the property existing in the fully developed 

 organ al the period when the experiment was 

 begun ; and hence it is plain, and conformable 

 to all analogy, that contractility is a property 

 depending for its integrity on a healthy state of 

 nutrition, which in its turn requires for its 

 support the due exercise of the property it 

 confers. 



It might, perhaps, be argued by one dis- 

 posed to uphold the electrical hypothesis of 

 the nervous influence and muscular power, 

 that in the foregoing experiments the galvanism 

 supplied the place of the intercepted nervous 

 communication, by directly furnishing the 

 muscles with the endowment of contractility ; 

 and it is not easy to meet the objection by any 

 decided proof to the contrary. It would be 

 very difficult to induce oft-repeated contractions 

 in a paraly-ed muscle by any other than elec- 

 trical agency ; but the refutation of this view 

 will be found in the general arguments against 

 the identity of the nervous influence with any 

 form of electricity. 



Viewed by the light of this and other allied 

 experiments, the variation found in the state of 

 nutrition of paralyzed limbs is easily accounted 

 for. In cerebral paralysis the muscles are still 

 subject to contraction in obedience to reflected 

 stimuli through the spinal cord, while in the 

 complete spinal palsy and that arising from 

 disease of the nerves, they are never excited to 

 action ; whence their firmness in the former 

 compared with their impoverishment in the 

 latter case. In the paralysis of the lower limbs 

 so graphically described by Pott, and resulting 

 from disease propagated to the cord from the 

 vertebrae, the early symptoms are those of 

 irritation, and consist rather of irregular con- 

 tractions, probably in part reflex, and which 

 the patient is unable to control, than of any 

 diminution of actual power in the limbs; and 

 it is constantly remarked that in this stage there 

 is no loss of size in the affected parts, but 

 rather that in the midst of a general emaciation 

 consequent on the patient's confinement, these 

 limbs retain their fullness, and even appear 

 hypertrophied. Should the malady advance to 

 disorganization of the cord, the muscles cease 

 to be excited. They become dead to all stimuli 

 except such as are topically applied, and being 

 never so stimulated, soon become flabby and 

 wasted. Thus it would appear that the spinal 

 cord in cerebral paralysis serves to keep up 

 contractility in the muscles, not by supplying 

 them with it, as from a source, but by exhaust- 

 ing them through the contractions it excites. 

 It is not a charger but an exhauster through its 



nerves ; and as exhaustion alternating with re- 

 accumulation is necessary for healthy nutrition, 

 and healthy nutrition induces contractility, it 

 becomes in such cases an important though 

 indirect agent in the maintenance of that pro- 

 perty in the muscles. There can be little doubt 

 that if muscles completely cut off from the 

 nervous centres were submitted to galvanic 

 agency at frequent intervals, they would not 

 decrease in size, and might, if already atrophied, 

 be even augmented in bulk and power ; and 

 perhaps some of the vaunted successes obtained 

 by galvanism and electricity may be explained 

 in this manner. 



There appears to be no argument nor esta- 

 blished fact on the other side which invalidates 

 the experiment of Dr. Reid, or which does not 

 admit of being explained on the ground which 

 that experiment substantiates ; and the whole 

 question is still further cleared by the singular 

 circumstance that has been often adduced, that 

 foetuses born without brain or cord may have 

 their muscular system developed and active. 



If, to what has now been advanced, there 

 be added the evidence before adduced, that 

 this is a property inherent in the very structure 

 of muscle, and that it is capable of being 

 exerted therein independently of all communi- 

 cation with other tissues, it will probably no 

 longer remain doubtful that it is a property 

 belonging to muscle as a tissue, and that it 

 only requires for its perfection that nutrition 

 should be perfect. Whatever interrupts nutri- 

 tion interferes with it, and it matters little 

 whether such interruption arise from the want 

 of its own exercise or from deficiency of arterial 

 supply, arising from causes either local or 

 general. Inertness of a muscle, whether the 

 consequence of diseased nerves or otherwise, 

 will be attended with more or less atrophy and 

 weakness, according to its degree, and to that 

 alone. 



For full information concerning the varieties 

 in the intensity of this power, and in its dura- 

 bility in muscles after systemic death or after 

 their removal from connexion with the nervous 

 and vascular systems, the render is referred to 

 the article IRRITABILITY. 



I would merely remark in corroboration of 

 the views there maintained, that in the animal 

 series the size of the elementary fibres and the 

 consequent amount of their vascular supply, 

 independently of the more or less arterial 

 quality of the blood, is accurately proportioned 

 to their irritability. Thus Birds, whose irrita- 

 bility is most exalted and most evanescent, 

 have the smallest fibres and the most richly 

 supplied with blood, while Reptiles, Fish, and 

 Crustacea, in which the irr, lability is most 

 enduring, have fibres of large dimensions and 

 provided with a vascular web of small com- 

 parative size (fig, 286, art. MUSCLE). The 

 same is true as regards the heart compared 

 with the voluntary muscles. 



b. Of the stimuli of muscle. The stimuli 

 which induce contraction have been classed 

 into remote and immediate. Properly speaking, 

 tiie remote stimuli are stimuli to the nerves and 

 not to the muscles : they cause a change in the 



