1909.] Cortical Lamination, etc., in Brain of Marmoset. 127 



surface, where the post central and limbic types adjoin it, it is not difficult 

 to determine the border line, but anteriorly and posteriorly, and inferiorly on 

 the dorsal surface, tlie type becomes less characteristic, and gradually its 

 distinctive character is lost as it merges into the intermediate indefinite 

 areas which surround it. The lamination is seen in its most typical form in 

 the posterior part of the area, near the postero-mesial border. 



Characteristics. — The cortex measures about I'o mm. in depth, the 

 molecular layer 0"1 mm., the pyramidal layer about 0"75 mm., the zone in 

 which the Betz cells lie about 0'2 mm., and the polymorph layer 0"3 mm. to 

 0"4 mm. The pyramidal cells are rather larger and less regularly and closely 

 arranged than in most other parts of the neopallium. Scattered granule 

 cells are found among them, but they do not form a separate layer. Below 

 the pyramids, lying in a pallid zone, there is a well-marked line of Betz 

 cells, the largest of which measure from 50 to 60 ix. These Betz cells, and 

 the absence of a granule layer, are the most marked characteristics of this 

 area. 



Motor Area B {fig. 4) lies below the motor area A between it and the 

 Sylvian fissure. On stimulation, movements of the jaw and mouth occur as 

 described in the account of the stimulation experiments, but it shows 

 a marked difference to the type just described in its histological details. 

 The molecular layer measures 01 to 0"15 mm., the pyramidal layer about 

 0"75 mm., the pallid zone about O'l mm., the granule layer 0'3 to 0'4 mm., 

 and the polymorph layer about 0'3 mm. The presence of a distinct band of 

 granules specially distinguishes it from the cortex above. There is also 



Motor A. 



WW 



Temporal. 



Motor B 



V V V V V V 



V V V V V V 



V V V V V V 



V V V V V V 



Visual. 



Post-central. 



// // // // // // 

 // // // // // // 

 // // // // // // 



Olfactory. 



0 0 0 O O 



0 © O O 0 

 O O O 0 O 



Limbic 



Key to diagrammatic representation of different types of cortex in figs. 1 and 2. 



L 2 



