30 STUDIES ON THE CENTRAL NERVOUS SYSTEM 



recognise the shape and size of the objects and to distin- 

 guish two points apphed simultaneously (discrimination). 

 Amongst other things the function of stereognosis is ren- 

 dered possible by the impulses conducted in this part of the 

 spinal cord. The other form serves more for feeling and is 

 more vital, while the former is more intellectual in character. 

 Hence they are opposed to one another and are called the 

 ^ Agnostic" and the ^ Vital" sensibility. 



All these sensory stimuli are sent upwards to the optic 

 thalamus, which is a centre where sensory functions are 

 associated. From the optic thalamus they are sent to the 

 cortex of the brain and meet there with many other stimuli 

 of different qualities. 



The way, however, in which these two systems are spread 

 throughout the central nervous system differs greatly. 

 The construction of the socalled gnostic sensibility is simple 

 as compared with the other. It is composed of three well- 

 known neurons. The first is the tract in the posterior 

 column, the second is the mesial fillet, the third the radiation 

 between the optic thalamus and the cortex. This tract 

 ends in the gyrus centralis posterior. The pathway for 

 vital sensibility is more complex. As above mentioned, the 

 second neuron begins immediately after the first neuron has 

 entered the spinal cord. Several of these stimuli are con- 

 ducted through the socalled spino-thalamic tract, but many 

 of them are also led by short pathways, connecting the gray 

 substance of different levels of the spinal cord, the oblongata 

 and the midbrain. There is not much known about the 

 termination of vital sensibility in the cortex, but we are sure, 

 that these fibres have a large and diffuse projection in the 

 cortex of the brain. A great part of the cortex cerebri may 

 be destroyed in men and in animals without causing any 

 defect to vital sensibility. In opposition to this, a circum- 

 scribed destruction of the sensory cortex, by gunshot wounds 

 for example or by a tumour, may cause clear disorders of the 



