PATHOLOGY OF SENSIBILITY 37 



By careful preparation Bolk followed the fibres of the various 

 posterior roots up into the skin. 



The principle of segmentation in the spinal cord is clearest 

 in vital sensibility. In syringomyelia, for example, a dis- 

 ease in which a tumour, composed of gliacells, chiefly grows 

 in the gray substance, there are amongst other things anal- 

 getic and thermo-anaesthetic areas in the skin, which may 

 show the same form as the dermatoms. 



There are also affections in which only gnostic, non- 

 autonomic sensibility suffers. A good example of this is 

 pernicious anaemia. A certain percentage of patients 

 suffering from this blood disease has symptoms of affection 

 of the central nervous system. In the early stages of the 

 disease one may often see disturbances of deep sensibility 

 and of finer touch in the legs, the other sensory functions 

 being normal. This is explained by the fact, that in these 

 cases there is only a parenchymatous degeneration of the 

 posterior columns, without any affection of the posterior 

 roots. In later periods of this disease the lateral columns 

 are also suffering and other symptoms appear. 



In most diseases of the spinal cord both non-autonomic 

 and vital sensibility are affected. In tabes, for instance, all 

 kinds of sensibility may suffer. This can easily be under- 

 stood when we remember, that in tabes the posterior roots 

 themselves are affected. In these roots all the fibres of the 

 different sensory qualities lie close to one another and hence 

 all suffer together by spirochaetosis. 



In tumours, which press on the outside of the spinal cord, 

 the disturbances of sensation vary greatly. To localise the 

 exact level of the tumour we regularly use these dermatoms. 

 When, for example, a tumour presses on the first thoracal 

 segment, disorders of sensibility arise in such a form that 

 the upper border of the disturbed area is the same as the 

 lower border of the next segment which is free. So it seems 

 to be very simple to localise tumours of the spinal cord and 

 to send them with a correct diagnosis to the surgeon. But 



