308 



PHYSIOLOGY 



nerve fibre (Fig. 147). The axis cylinder of the nerve fibre can be regarded 

 as made up of fine fibrillse embedded in an interfibrillar substance. At the 

 nodes of Ranvier the interfibrillar substance is interrupted, the fibrillse alone 

 extending into the next internode and representing the continuous structure 

 which determines the conducting power of the nerve fibre. In the nerve- 

 cell the fibrillse occupy all the space between the Nissl bodies, passing from 

 dendrite to dendrite, and many of them from all the dendrites and all parts 

 of the cell sweeping through the axon hillock to form the fibrillee of the nerve 

 fibre. The existence of these fibrillar structures in nerve-cell and nerve 



Ax 



FIG. 147. Part of an anterior cornual 

 cell from the calf's spinal cord, 

 stained to show neuro fibrils. 

 (BETHE.) 



Ax, axon; a, b, c, dendrites. 



FIG. 148. Arborisation of 

 collaterals from the pos- 

 terior root- fibres round 

 the cells of the posterior 

 horn. (RAMON Y CAJAL.) 



fibre is accepted by most histologists. The question, however, of the con- 

 nection between the fibrillse of one axon and those of the next neuron, i.e. 

 the histology of the synapse, presents much greater difficulties and has 

 excited much difference of opinion. If we examine a nerve-cell such as a 

 cell of Purkinje of the cerebellum, or a cell of Clarke's column in the cord, 

 we find that it is surrounded by a thick basket-work of fibres which are the 

 arborisations or end terminations of the axons which pass to the cell to 

 enter into functional relationships with it (Figs. 148 and 149). This peri- 

 cellular network is of great extent and may equal in total diameter the 

 diameter of the cell itself. Whether the basket-work is really a network, 



