406 Giant Cells of tlie Bonnet Monkey 



volution. Another small group of giant eells appears in a corresponding 

 position, after an interval of 10 sections (0.5 mm. higher on the sur- 

 face) contiguous to the external aspect of the corona radiata of the 

 ascending frontal convolution. This arrangement of the giant cells in 

 groups does not obtain within the fissure of Rolando, but they appear 

 here as a continuous layer in gradually increasing numbers from below 

 "upward. Xor is there any further appearance of grouping of the giant 

 cells on the external aspect of the corona radiata of the ascending 

 frontal convolution, but from this point upward they extend farther 

 and farther forward until in the level of the anterior limb of the frontal 

 sulcus they cover the entire antero-posterior extent of the external aspect 

 of the corona radiata of the ascending frontal convolution. At a slightly 

 higher level the giant cells entirely envelope this process of the corona 

 radiata ; that is, they are present upon its posterior, external and 

 anterior aspects, and as we reach still higher levels extend a short dis- 

 tance forward in contiguity with the external surface of the corona 

 radiata of the frontal lobe (Fig. 3). 



This arrangement is maintained throughout the remainder of the 

 upward extension of the corona radiata, which, in the monkey, cor- 

 responds to the cortex of the ascending frontal and the posterior portion 

 of the superior frontal convolution (Fig. 1). 



This distribution of the giant cells upon the external surface of the 

 brain is by no means uniform. They are most numerous within the 

 sulcus of Eolando and in that portion of the cortex covering the ascend- 

 ing frontal convolution, while in the cortex of the superior frontal they 

 are more Scattered. Within the sulcus of Eolando they extend to the 

 base of the sulcus, but are confined entirely to the anterior lip; that is, 

 they nowhere pass beneath the base of the fissure to the parietal lip. 



There are two small groups of large cells in the cortex of the ascend- 

 ing parietal convolution : one just above the lower extremity of the 

 intra-parietal fissure appearing in fourteen consecutive sections, the 

 cells diminishing in number and size from below upward. These cells 

 extend into the intra-parietal fissure but not into the fissure of Rolando. 

 There is another small group of large cells in the cortex of the upper 

 ■extremity of the ascending parietal convolution, only present in four 

 sections. With the exception of a few very large cells within the intra- 

 parietal fissure, the cells described in the cortex of the ascending 

 parietal convolution are much smaller than the majority of the giant 

 cells anterior to the fissure of Rolando. Those anterior to Rolando 

 measure from 20 to 60 microns in length bv from 10 to 40 microns in 



