DEVELOPMENT OF NERVE ELEMENTS. 1 65 



cortex of the adult, which I shall later describe, are 

 rightly interpreted, growth in that locality must be 

 going on between the twentieth and fortieth years, and, 

 judging from Venn's observations on the enlargement 

 of the head, is extended over the first half of that 

 interval at least. 



Much interest has always attached to the determina- 

 tion of the time when the central system was structur- 

 ally completed. As might be anticipated, the various 

 portions are completed at very different periods, accord- 

 ing to their functions, and hence all statements on this 

 head require to be made in detail. Schiller J counted 

 the number of nerve fibres in the oculo-motor nerves of 

 cats at birth and at later ages. His results are given in 

 summary in the table which follows. 



TABLE 37. SHOWING THE AVERAGE NUMBER OF FIBRES FOUND 



IN EACH OF THE OCULO-MOTOR NERVES OF CATS, FROM 



BIRTH TO EIGHTEEN MONTHS OF AGE. (Schiller.} 



This table shows that between birth and matu- 

 rity there is in the cat a very slight increase in the 

 number of fibres composing the oculo-motor nerve. 

 The author explains the slightly smaller number found 

 at the earlier ages as due to the small size of the 

 youngest fibres, which are thereby made exceedingly 



T Schiller, Compt. Rend. Acad. d. St., Paris, 1889. 



