244 THE GROWTH OF THE BRAIN. 



layers has increased, and this too despite the fact that 

 the individual fibres have grown larger. At the first 

 age the number is greatest in the anterior central gyrus 

 and the parts behind it. The increase is greatest in the 

 outer layer, next in the middle, and least in the inner 

 one, so that, according to this, the increase in the 

 number of fibres progresses from the deepest layer 

 towards the surface. When, on the other hand, the 

 development at each locality is followed through a. 

 number of years, a different, though concordant, series 

 of changes is observed, and these are shown in the 

 three tables given below. 



Chart C, F.3s., is a region late to develop, and the 

 growth there is even and regular. Chart D, V. C.d., 

 shows a region well developed at an early age, and 

 since, therefore, the period for this is probably variable, 

 it is not surprising that the curve is uneven ; while Chart 

 E, T.is., develops more slowly and is again regular. The 

 proportionate increase in the several layers is greatest 

 for those that begin earliest. In the motor areas (F.3s. 

 and V.C.d.) there is a decrease in the number of fibres 

 after the thirty-third year, this being most marked in 

 V.C.d. In T.i.s. this diminution is delayed. 



In the new-born child, Vulpius found no medullated 

 fibres in the cortex. In the white substance of the 

 anterior central gyrus alone some medullated fibres 

 were found. The first tangential fibres appear in the 

 inner and outer layers of a child at four and a half 

 months and in the middle layer at eight months. 



Along this same line are the observations of Kaes, 1 

 who directed attention principally to the layers II and 

 and III, Fig. 47 (the middle layer of Vulpius), and aimed 

 to determine how late in life increase in the medullated 

 fibres could be here followed. His method was to 



1 Kaes, Archiv. f. Psychiat. u. Ncrvcnkrank, Bd. xxv. 1894, 



