862 THE SPINAL CORD. 



simply to the section of the roots in the dorsal column. After low thoracic 

 semisection, the angle of galvanometric deflection ohtained from the cord a few 

 segments higher was, under sciatic faradisation, less when the nerve was 

 homonymous than when contra-lateral. In the eight observations the defect of 

 deflection on the uncrossed side varied between 26 and 78 per cent., and was 

 presumably for the most part referable to the severance of the root-fibres in the 

 dorsal column. A semisection some segments behind the faradised cut end 

 of the cord in the thoracic region abolished the action current, however, in the 

 homonymous sciatic nerve. What relation the degree of galvanometric 

 deflection bears to the aggregate size or number of a spinal fibre system is 

 not ascertained. One would think it more influenced by number of fibres than 

 by size of fibres. For one and the same fibre system it presumably varies in a 

 direct sense with the physiological intensity of the reaction, but in what ratio 

 is difficult to estimate. One difficulty in interpreting in terms of normal 

 spinal conduction the spread of action-current, is the fact of double conduction. 

 Thus, when the cord is excited in the lower thoracic region, the chief 

 channel of spread of action currents both up and down seems to be the dorsal 

 column. 



Observations, taking note of not only the relative amount but also the 

 physiological quality of the reactions for which the cord is blocked 

 or still patent after semisection, find special difficulty in regard to the 

 quality of the long dorsal column path. Its severance has in various 

 hands, 1 and practised at various levels, made no striking alteration 

 at all either in movement or in signs interpretable of sensation. There 

 is clear evidence that the path belongs to an afferent chain of which the 

 next neural link begins in the dorsal column nuclei of the bulb, and 

 leads in the main by the crossed mesial fillet to the thalamus and, less 

 directly, to cerebral cortex (especially its post-central and fornicate 

 gyri). The clinical evidence collected about the physiological quality 

 of the dorsal column is of negative character. Lesions in it, either 

 unilateral or bilateral, have occurred without any obvious disturbance 

 of sensation ; at utmost a slight clumsiness in the movements of 

 hand or foot. After arrest of the circulation in the lower region of 

 the spinal cord, Mlinzer and Wiener 2 found that " pathic " stimuli 

 applied to the skin of the hind-limbs were not effective to provoke 

 signs of sensation, and Langendorff, 3 that excitation of the afferent 

 roots as well as light tactile stimuli to the skin, even under slight 

 strychnisation, remained ineffective. The argument from these stasis 

 experiments rests on the supposed earlier paralysis of grey than of white 

 matter by the stasis, and infers that, therefore, tactual and painful 

 sensorial impulses must embouch into grey matter near the entrance of 

 the root conveying them into the cord ; the further inference is that the 

 long dorsal column path is not the path used in the reactions of touch 

 and pain. But I have seen strong pathic stimuli evoke reactions when 

 applied to the skin of the hind-limbs at a time when, by arrest of 

 the circulation in the cord, those limbs themselves were flaccid and 

 paralytic; here the reaction probably occurred vid the long dorsal- 

 column path. After transection of all the columns, except the dorsal, 

 signs of sensation can still be evoked from the parts innervated by 

 segments posterior to the section, as also from the cerebral face of a 



1 Miescher, Arb. a. d. physiol. Anst. zu Leipzig, 1870, S. 404 ; Nawrocki, ibid., 1871, 

 S. 585; Dittmar, ibid., 1873, S. 479; Woroschiloff, ibid., 1874, S. 99. 

 - Arch./, exper. Path. u. Pharmakol., Leipzig, 1895, Bd. xxxv. S. 114. 

 3 Arch. f. d. ges. Physiol., Bonn, 1898, Bd. lxxi. S. 401. 



