36 STUDIES ON THE CENTRAL NERVOUS SYSTEM 



cortex of the brain in a diffuse way. The principle of an 

 exact locahzation is not found here, on the contrary, these 

 stimuli are diffusively spread throughout several parts of the 

 central nervous system. In these pathways stimuli are 

 conducted for vital sensibility, which at a high level of the 

 brain may cause sensory feelings. 



It is clear that both these forms of sensibility always work 

 together in the cortex cerebri and that they constantly in- 

 teract. It is this constant separate cooperation, that ena- 

 bles us to form ideas of the outer-world, in so far as this is 

 possible by sensory stimuli. 



You understand that an exact knowledge of the organisa- 

 tion of sensibility helps greatly to diagnose diseases of the 

 nervous system and to localise pathological processes in the 

 brain and spinal cord. In this connection I remind you 

 especially of traumatic lesions, infectious diseases, tumours 

 and sclerotic degenerations. From all these clinical patho- 

 logical syndroms, I shall take tumours, because these form a 

 part of neurology, where biological research and practical 

 application cooperate to attain therapeutic results. From 

 these tumours I shall select those of the spinal cord. 



You know that tumours of the spinal cord may cause dis- 

 orders of motility, of sensibility and of autonomic functions. 

 The state of these disturbances depends on the level of the 

 tumour in the spinal cord. Above all, the disturbances of 

 sensibility enable us to localise the exact level of a tumour. 

 The doctrine of the segmental anatomy has made this pos- 

 sible. All the sensory impulses enter the spinal cord by the 

 posterior roots and we know by the investigations of Bolk, 

 Sherrington, Kocher and others, that each root and each 

 segment of the spinal cord belongs to a well localised and 

 well known part of the skin. The part of the skin which is 

 innervated by a segmental root is called a dermatom. 

 There are several schemes indicating how these dermatoms 

 are distributed. In Holland we always use Bolk's diagrams. 



