THE GROWTH OF THE BRAIN. 



TABLE 33. SHOWING THE VOLUMES OF THE LARGEST CELL- 

 BODIES IN THE VENTRAL HORN OF THE CERVICAL CORD 

 OF MAN. (Based on Kaiser's records of the mean dia- 

 meters.) 



The volume 7oo^ 3 , in the foetus of four weeks, is taken from His, 

 and the figures represent multiples of that volume. 



It shows a rapid increase in the volume of the largest 

 cells during the earlier months before birth. Between 

 birth and maturity the change is slight, and as a conse- 

 quence these figures suggest that growth after birth is 

 mainly due to some cause other than the further 

 enlargement of the cell-bodies most developed at that 

 time. 



As a rule, when the size of nerve cells is stated in the 

 text-books the measurements apply to the cell-body 

 only, and the changes in this are expressed in the fore- 

 going table, yet it is desirable to insist on the genetic 

 connection between the cell-body and the neuron, and 

 so the increase of the latter should be considered at 

 the same time. In the mixed peripheral nerve of a 

 new-bom child the diameter of the fibres, including 

 the sheath, was found (Westphal) to be i'2-2 //, 

 for the smallest, up to 7-8 /JL for the largest, with an 



