60 



THE NERVOUS SYSTEM 



These important networks are now under active discussion; their 

 function is by no means understood. 



The neurone theory of the structure and action of the nervous system 

 supposes that even in the adult this system is made up entirely of distinct 

 units called neurones, which do not connect structurally save by contact. 

 Between them are the recondite gaps called synapses, to which some 



FIG. 29 



Diagram of some of the neurones concerned in the central nervous system: A, cortex cerebri; 

 B, spinal cord; C, muscle-cells and the teleodendrites of a motor spinal neurone; D, a peripheral 

 afferent (sensory?) surface; G, spinal ganglion; a, the neuraxone of a corticospinal neurone; 6, 

 the teleodendrites of the same in the anterior gray horn; c, the neuraxone of an afferent spinal 

 neurone; d, the peripheral process of the same; e, the bifurcation of the same; f, the teleoden- 

 drites of the same connecting with the dendrites of another neurone, g, in the brain somewhere. 

 (Ramon y Cajal.) 



investigators attribute a psychical nature. A neurone consists of a nerve- 

 cell and nerve-fibers, of various numbers and lengths and modes of 

 branching, extending from it. One of these projections is usually longer 

 and more definite and direct than the others, and is called the neuraxis 

 or neuraxone. This neuraxis, marked also by its uniform diameter, 



