SYMPATHETIC NERVE. 



457 



By the term centre, Volkmann seems to mean 

 an organ which serves as a regulating appa- 

 ratus, and by which several separate and 

 simple acts are combined into a single com- 

 plex organic act. The contraction of a muscle 

 is a simple act ; in the act of respiration we 

 have the contractions of many muscles com- 

 bined into a single complex act, their com- 

 bination being dependant on a power situated 

 in the medulla oblongata, which part of the 

 nervous system is therefore termed their cen- 

 tral organ. The question then in regard to 

 the independence of the sympathetic is, whe- 

 ther, in the sphere of the organic nerves, 

 there be such combinations, and whether these 

 have their centre in the brain and spinal cord, 

 or in the sympathetic. The brain is the centre 

 of all psychical acts ; it is therefore evident 

 that the sympathetic, in so far as regards all 

 the phenomena of sensation occurring in its 

 sphere, must be regarded as dependent on the 

 brain. But after the brain and spinal cord 

 have been destroyed, does the sympathetic 

 still remain active, and in such a state of 

 activity as implies the co-operation of a cen- 

 tral organ ? Muscular motion implies the 

 activity of the motor nerves, and the activity 

 of those muscles which are supplied by the 

 sympathetic must imply the activity of sym- 

 pathetic nerve fibres. The action of the 

 heart, however, as well as the circulation, 

 sometimes continues for weeks after the de- 

 struction of the central masses of the nervous 

 system. Thus Bidder removed with great 

 care the arches of the second cervical ver- 

 tebra, so that little blood was lost during the 

 operation, and then completely destroyed the 

 spinal cord. Frogs treated in* this way often 

 lived six weeks, sometimes ten, the circula- 

 tion, as seen in the web of the foot, remain- 

 ing at the same time active, and not differ- 

 ing from that in uninjured frogs. The heart 

 beat powerfully and quickly: in a freshly- 

 killed frog, in winter, the heart pulsated thirty- 

 fiva times in the minute ; while in a frog, the 

 spinal cord of which had been destroyed 

 twenty-six days previously, the pulsations 

 were forty per minute. When the brain and 

 spinal cord were destroyed, the medulla ob- 

 longata being left, frogs were retained in life 

 until the sixth day ; and when the entire cen- 

 tral organs of the nervous system were re- 

 moved, they lived until the second day; the 

 rapidly ensuing death in the latter case being 

 due, according to Volkmann, to the effects 

 produced upon the respiration. Within a few 

 weeks after the destruction of the spinal cord 

 the muscles of animal life were found to have 

 lost their irritability in a marked degree, and 

 still later no contraction could be produced 

 in them by application of chemical or me- 

 chanical stimuli ; the heart, however, in such 

 cases still continued to pulsate eleven times 

 in the minute, and retained its property of 

 responding to external stimuli. The intes- 

 tinal canal, in like manner, retained its irrita- 

 bility ; application of stimuli giving rise to 

 contractions which were sometimes of a local 

 nature, at other times extended for a con- 



siderable distance on either side of the part 

 stimulated. Digestion, in like manner, suffers 

 but little from destruction of the central 

 parts of the nervous system ; healthy frogs, 

 and others, which had been operated upon, 

 were, after being starved for a considerable 

 time, fed with worms, and kept in separate 

 glasses. In the one, as well as in the other, 

 the worms were found after twenty-four 

 hours to be fully digested, and the stomach 

 and duodenum were filled with coloured 

 mucus ; such was observed to be the case 

 even in animals whose spinal cord had 

 been destroyed twenty-six days previously. 

 The secretion of urine also continues : when 

 in animals in which the brain or spinal cord 

 had been removed, the bladder was emptied 

 by external pressure upon the walls of the 

 abdomen, in a short time it again became filled 

 and distended to an enormous size, unless 

 emptied in the way just mentioned. It had 

 been observed by Valentin and Stilling that 

 after destruction of the spinal cord in the 

 frog, different derangements in the nutritive 

 processes ensued ; there were frequently ob- 

 served dropsical swellings, especially of the 

 limbs. On these also, sores formed, which 

 often penetrated as far as the bones. In re- 

 ference to these results, Volkmann states 

 that they are, as shown by Bidder, chiefly 

 accidental. Bidder found that when the 

 bottom of the vessels in which the frogs were 

 kept was covered, not with water, but with 

 moist grass or moss, no such degenerations 

 ensued. The rapid death which ensues in 

 warm-blooded animals, when operated upon 

 in the above manner, depends, according to 

 Volkmann, upon the difficulty of sufficiently 

 keeping up the respiration by artificial means, 

 as well as upon the loss of blood and diminu- 

 tion of animal heat. The circumstance, then, 

 that a certain number of the vital phenomena 

 disappear suddenly and irrevocably after de- 

 struction of the spinal cord and brain, while 

 others continue for a greater or shorter 

 time, and this very perfectly, can only de- 

 pend, according to Volkmann, upon the cir- 

 cumstance that the brain and spinal cord is 

 a necessary condition for the existence of the 

 former, but not for that of the latter. If the 

 latter depend upon certain nervous organs, 

 and if the nerves of the vegetative organs do 

 not require, as a fundamental condition of 

 their activity, the presence of the brain and 

 spinal cord, the only possible centres on which 

 they can depend for this are the ganglia of 

 the sympathetic. The sympathetic and its 

 ganglia, then, constitute, according to Volk- 

 mann, an independent whole, from which 

 proceed the impulses to as well as the regula- 

 tion of those actions which continue after 

 the brain and spinal cord have been destroyed, 

 and which notwithstanding require the co- 

 operation of a central organ. That the move- 

 ments in question require such an organ, and 

 are not produced by the mere stimulus of the 

 blood, faeces, air, &c., in the same way as the 

 twitchings of the muscles in a frog's leg are 

 produced by galvanism, is shown, according 



