?2lN 



PHYSIOLOGY OF THE NERVOUS SYSTEM. 



posture through the influence of the spinal 

 cord, but, imined lately this organ has been 

 removed, the limbs fall apart from the loss of 

 the controlling and co-ordinating influence of 

 the nervous centres. And careful examination 

 of the muscles in such a case as this will show 

 that the molecular phenomena which charac- 

 terise passive contraction continue in the mus- 

 cular fibres. The state of rigor mortis, which 

 is analogous to that of tone, comes on just as 

 readily in animals which have been deprived 

 of the brain and spinal cord, as in those 

 in which these centres have been undisturbed 

 before death. In short, healthy nutrition sup- 

 plies all the conditions necessary for the main- 

 tenance of tone or passive contraction ; nor is 

 the spinal cord (although itself healthy) able to 

 preserve the tense condition of the muscles, if 

 they are not well nourished. 



These remarks apply equally to Dr. Hall's 

 doctrine, that the spinal cord is a direct source 

 of irritability to the muscular system. The 

 same arguments which prove that tone is not 

 derived from it are of equal weight with refe- 

 rence to irritability. 



It cannot be admitted as an argument in 

 favour of the view which derives muscular irri- 

 tability from the spinal cord, that muscles lose 

 their firmness and waste, when they have been 

 for some time separated from their proper ner- 

 vous connections. They suffer, in this way, 

 merely for want of a proper amount of exercise, 

 which they cannot obtain in consequence of 

 the influence of the will being cut off from the 

 limb. If, however, the paralysed limb be ex- 

 ercised artificially, as by the galvanic current, 

 their nutrition and their plumpness may be 

 preserved. For this important observation we 

 are indebted to Dr. John Reid, who likewise 

 called attention to the confirmatory fact, that, 

 in those palsies with which there is combined 

 more or less of irritation of the nervous centre, 

 the muscles do not suffer so much in their 

 nutrition, in consequence of the exercise they 

 undergo in the starlings so frequently excited in 

 them by the central irritation. This is not 

 unfrequently seen in cases of paraplegia from 

 irritant disease of the spinal cord. 



The supposition that the spinal cord might 

 be the source of irritability to ihe muscles led 

 Dr. Hall to the very extraordinary inference, 

 that in hemiplegic paralysis, in which the in- 

 fluence of the brain is cut off from certain 

 muscles, while thai of the cord remained, the 

 irritability of those muscles becomes augmented. 

 He arrives at this conclusion by the following 

 line of argument: assuming the cord to be the 

 source of the irritability of the muscles, the 

 brain may then evidently be looked upon as 

 the exhauster of that irritability in the volun- 

 tary actions; if, then, the influence of the 

 brain be cut off, it naturally follows that, as the 

 great agenl of exhaustion has lost its power, 

 the irritability, which is ever, as it were, flow- 

 ing from the cord, will accumulate in the 

 muscles. From numerous experiments I am 

 enabled to state that in nearly all the cases of 

 hemiplegic paralysis from cerebral lesion there 

 is no evidence of any augmentation of the 



irritability of the muscles of the palsied limbs. 

 If the readiness with which they will respond 

 to the galvanic stimulus be taken as a tesl, 

 it may on the other hand be stated very 

 confidently that there is evidence of the di- 

 minution of ihe irritability of the paralysed 

 muscles, for in nearly all these cases the same 

 current being passed through both sound and 

 palsied limbs at the same lime, ihe latter have 

 contracted either not at all or with very litlle 

 power as compared with the healthy limbs. 



But there are exceptions to tins: in some 

 cases (and only in those in which there is 

 more or less rigidityof the paralysed muscles) 

 these muscles respond to the galvanic stimulus 

 with more force and readiness than the sound 

 ones. In these cases the palsied muscles are 

 kept in a state of excitement by some irritant 

 disease within the cranium, and this constant 

 condition of more or less active contraction 

 augments the nutrition, and therefore the irri- 

 tability of the muscles. 



It seems, however, most probable thai in all 

 the cases of paralysis, the excitability of the 

 muscles to the galvanic stimulus is dependent 

 not so much upon any change in the condilion 

 of die muscles ihemselves as upon ihe state of 

 the nerves. If the nervous force in ihe nerves 

 on the palsied side be depressed, the galvanic 

 stimulus will produce little or no effect upon 

 the muscles of thai side, whilsl those of the 

 other side will be distinclly exciled: bul should 

 the nerves participate in any excitement propa- 

 gated to them from disease within the cranium, 

 as in red softening, or an irritating tumor, or a 

 contracting cyst, they will ihen respond lo ihe 

 galvanic current more readily than ihose of the 

 opposite side.* 



I have thus endeavoured lo show thai the 

 spinal cord is a centre of nervous actions, men- 

 tal and physical, to all parts which derive nerves 

 J'rom it, ihe mental actions, however, requiring 

 its association with the brain. Whatever phy- 

 sical nervous actions occur in parts whose 

 nerves are spinal, must be referred to the cord 

 alone ; and whatever mental nervous actions 

 occur through the agency of spinal nerves must 

 be referred lo the cord in conjunction with the 

 brain. 



Of the office of the columns of the cord. I 

 shall now inquire whether the parts into which 

 ihe anatomist can divide the spinal cord have 

 special functions. These parts are, on each 

 side of the median plane, an antero-lateral co- 

 lumn and a posterior column. It has been a 

 very prevalent opinion lhat the anlero-lateral 

 column corresponds in function with the ante- 

 rior roots of the spinal nerves, and lhal ihe pos- 

 lerior column corresponds with the posterior 

 roots. This doctrine might have had a good 

 foundation if il could be proved lhal ihe posterior 

 or sensitive roots were implanted solely in ihe 



* I have discussed this subject more at large in 

 a paper presented to the Royal Medico-Chirurgical 

 Society in June last, and which will appear in the 

 forthcoming volume of its Transactions. August, 

 1847. 



