DISEASES OF THE NERVOUS SYSTEM. 279 



interwoven into the network of the neuroglia fibrils. These 

 are termed the neuroglia cells (Klein). 



Now, the nerve-cells alone are capable of exhibiting inde- 

 pendent nervous activity. 



They are the receivers of impressions and the generators 

 of nerve-force, and therefore the true physiological nerve- 

 centres are exclusively confined to the grey matter. The 

 nerve-fibres only serve to conduct impulses to and from the 

 nerve-centres with which they are in connection. 



Cerebro-Spinal System. — On a vertical section of the 

 hemispheres of the cerebrum, each convolution of the brain 

 shows a white centre composed of meduUated nerve-fibres 

 and a grey cortex. 



The white matter of the convolution is arranged (1) as a 

 central mass — the centrum ovale, from which the lamina of 

 white matter for each convolution branches off", and (2) the 

 commissure of white matter between the two hemispheres, 

 i.e. J the corpus callosum, and the anterior commissure 

 (Klein). 



The centrum ovale consists of {a) tracts of meduUated 

 nerve-fibres which connect the convolutions of the same 

 hemisphere with one another, and {h) those passing 

 between the convolutions on the one hand, and the 

 thalamus opticus, the pons varolii, and the medulla on the 

 other. 



From the whole of the cerebral surface, therefore, white 

 fibres radiate to the large ganglia at the base. 



A special part of the corpora striata, termed the internal 

 capsule, chiefly receives filaments from the anterior half of 

 the brain, and these are concerned in the transmission of 

 motor impulses. They pass through the * crusta ' of the 

 crura cerebri, and thence along the motor tracts of the cord. 

 The other ganglia at the base mainly receive fibres from 

 the posterior part of the brain, and are chiefly concerned 



