NATURE OF CONNECTION" BETWEEN NEURONS 349 



course of a nerve impulse according to Bethe is represented in the 

 accompanying diagram (Fig. 152). An impulse starting from the 

 periphery of the body travels up the distal process of the posterior 

 root ganglion- cell, passes either through the cell or directly to the 

 central process, and travels along this to the terminations of the 

 posterior root fibres round a posterior horn-cell. Here it passes into 

 the peri-cellular basket-work or axon network, thence into the Golgi 

 network and along the fibrillae of the cell out by the fibrillse of the axon 

 and so to a fresh synapse with a cell of the anterior horn. 



There are certain physiological difficulties in the acceptance of this 

 doctrine, of continuity through the central nervous system. Even 



FIG. 152. Schema of the neurofibrillar continuum, involved in an ordinary 

 reflex act in a vertebrate nervous system. (BETHE.) 



if it be true, it would not in any way upset the importance of the neuron 

 theory. Every plant or animal individual must be regarded as a proto- 

 plasmic continuum. With growth of the living matter, its metabolic 

 functions demand the dispersion of nuclear material through the 

 protoplasm, and this is effected by division of the nucleus. Considera- 

 tions of strength and rigidity demand the division of the protoplasm 

 into compartments or cells, which, at first at any rate, remain in proto- 

 plasmic continuity. This division has probably a further advantage 

 in that lesions of parts of the individual entail merely the death of the 

 cells immediately affected and do not necessarily spread to the whole 

 organism. Thus in the central nervous system injury to one axon 

 causes degeneration of the axon below the point of section, but the 

 degeneration stops short at the end arborisation and does not 

 spread into the next neuron. 1 we assume that, in consequence of the 

 straitness of the path, the propagation through the fibrillfe is 



