THE CENTRAL NERVOUS SYSTEM 787 



We cannot doubt that the spinal cord takes an important share in 

 the recovery of function after shock. But here again it would be 

 erroneous to conclude that everything is due to the cord. For Goltz 

 and Ewald have been able to keep dogs alive for long periods after 

 preliminary section of the cord in the cervical region and subsequent 

 removal of large portions of it. They find that even after destruction 

 of the lumbar and sacral regions of the cord the external sphincter of 

 the anus, striped and even voluntary muscle though it be, regains its 

 tone, although it is temporarily lost after the first cervical section. 

 The bladder ultimately recovers the power of emptying itself spon- 

 taneously and at regular intervals. A pregnant bitch in which the 

 lumbar enlargement and the whole cord below it to the cauda equina 

 had been removed, and therefore all the nerve-roots supplying 

 fibres to the uterus cut, whelped in a normal manner, and the 

 corresponding mammary glands behaved exactly as the rest. Diges- 

 tion went on as usual when practically nothing of the cord except 

 its cervical portion was left. Certain vaso-motor phenomena were 

 also observed which suggest that the sympathetic system, inde- 

 pendently of the cerebro-spinal system, is itself possessed of regula- 

 tive powers (p. 1 68). 



Secondly, we must not run into the opposite error, and assume, 

 without proof, that all the functions which the brain or cord is 

 capable of manifesting under abnormal circumstances are actually 

 exercised by either when, under ordinary conditions, it is working 

 along with and guiding, or being guided by, the other. For example, 

 in many animals certain of the reflex powers of the cord are, if not 

 increased, at all events more freely exercised when the controlling 

 influence of the higher centres has been cut off than when the central 

 nervous system is intact. 



Thirdly, there is another class of phenomena which we must make 

 allowance for, and perhaps more frequently in the case of patho- 

 logical lesions in man than in experimental lesions in the lower 

 animals. This is the class of ' irritative ' phenomena. The irrita- 

 tion set up by a blood-clot or a collection of pus, or in any other way, 

 in a wound of the grey or white matter, may cause a stimulation of 

 nervous tracts by which, for a time, the ' deficiency ' effects of the 

 lesion may be masked. 



In the fourth place, we must not hastily conclude that when no 

 obvious deficiency seems to follow the removal of a portion of 

 the central nervous system, the function of that portion must 

 necessarily be of such a nature as to give rise to no objective 

 signs. For there is reason to believe that, to a certain extent, 

 the function of one part may, in its absence, be vicariously per- 

 formed by another. 



Bearing in mind the cautions we have just been emphasizing, 

 we may broadly distinguish between the functions of the cord 

 (including the bulb) and those of the brain proper by saying 

 that the cord is essentially the seat of reflex actions, the brain 

 the seat of automatic actions and conscious prccesses. But 

 neither of these conceptions is entirely correct. Both err by 

 defect and by excess. The brain, it is true, is pre-eminently 

 automatic. The movements which are started in the grey 

 matter of the cerebral cortex are pre-eminently voluntary 



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