386 



THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



mately becomes converted into a secondary protoplasm. I 

 must certainly regard this surprising statement as having 

 been based on ambiguous specimens; for in sections of the 

 cortex of the cerebrum of new-born children the general dis- 

 tribution of the most clearly denned persistent forms is readily 

 and unmistakably exhibited. 



The formation of different concentric cortical layers depends 

 (1) upon the varying closeness of the arrangement, and (2) upon 

 the varying forms of the nerve corpuscles. The pyramidal 

 form (fig. 235, a 6) of the nerve corpuscles, which is the only 

 one admitted by some observers, as by Luys, Amdt, Stephany, 

 is the most common in the general five-laminated type of cortical 

 structure, and, as in fig. 234, fills the second layer, forming a 



Fig. 235. 



**] 



Fig. 235. , Ordinary fragmentary form of the pyramidal cells, con- 

 taining an angular nucleus and a branched apical process ; 6, true form 

 of the cortical corpuscles of the second and third layers represented by 

 a large cell of the formation of the cornu Ammonis with angular nu- 

 cleus; **, truncated apical process; *, the middle basal process; c, 

 the elements of the fourth cortical layer ; d, fusiform cortical body of 

 the fifth layer with fusiform nucleus ; e, the elements of the so-called 

 granule-layer of the cerebellar cortex. 



closely compressed series of small elements of 10 JJL in diameter ; 

 whilst in the third layer they are much more widely separated 

 from one another, and augment progressively till they attain the 



