AGE, GROWTH, AND DEATH 



FIG. ir. COPY OF THE ORIGINAL FIGURE 

 FROM THE MEMOIR OF DEITERS, in which the 

 proof of the origin of the nerve fibres directly 

 from the nerve cells was first published. The 

 memoir is one of the classics of anatomy. It 

 was issued posthumously, for the author died 

 young, to the great loss of science. The figure 

 represents a single isolated motor nerve cell 

 from the spinal cord of an ox. The single 

 unbranched axon, Ax, is readily distinguished 

 from the multiple branching dendrites, Den. 

 Nu is the spherical nucleus with its charac- 

 teristic central dot. 



grow, but the processes gradually grew out. 



usually named, 

 of the nerve fi- 

 bre as we en- 

 counter it in an 

 ordinary nerve. 

 This single 

 thread-like prolong- 

 ation of the nerve 

 cell is likewise con- 

 stituted by the liv- 

 ing protoplasm and 

 serves to carry the 

 impulses away from 

 the cell body and 

 transmit them ul- 

 timately to the mus- 

 cle fibres which are 

 to be stimulated to 

 contraction. In the 

 embryonic spinal 

 cord none of these 

 processes existed, 

 and the amount of 

 the protoplasm in 

 the nerve cell was 

 very much smaller. 

 As development pro- 

 gressed, not only did 

 the protoplasm body 

 Some of 



