40 



INTRODUCTION TO NEUROLOGY 



numerous very delicate longitudinally arranged neurofibrillae 

 embedded in a small amount of more fluid protoplasm. 



Fig. 5. Diagram of a motor neuron from the ventral column of gray 

 matter in the spinal cord. The cell body, dendrites, axon, collateral 

 branches, and terminal arborizations in muscle are all seen to be parts of a 

 single cell and together constitute the neuron: ah, Axon hillock free from 

 chromophilic bodies; ax, axon; c, cytoplasm of cell body containing chromo- 

 philic bodies, neurofibrils, and other constituents of protoplasm; d, den- 

 drites; m, myelin (medullary) sheath; m', striated muscle-fiber; n, nucleus; 

 n', nucleolus; nR, node of Ranvier where the axon divides; sf, collateral 

 branch; si, neurilemma (not apart of the neuron); tel, motor end-plate. 

 (After Barker, from Bailey's Histology.) 



The forms of neurons are infinitely diverse and appear to have 

 been determined by two chief factors; these are (1) the nutrition 



