422 PHYSIOLOGICAL SERIES. 



D. 629. The cerebellum, medulla oblongata, &c., of an Arabian 

 Baboon (Papio hanuulryas) , (c?). 



The floccular lobe of the left side is well preserved. 



0. C. 1338 A I>. 



D. 630. The left cerebral hemisphere of the same brain. 



This is a smaller hemisphere, and the sulci are .slightly 

 less complex than in the preceding examples (D. 626). 



The anterior part of the collateral is separated from the 

 posterior part, and is prolonged backward as an occipito- 

 parietal sulcus to join the inferior occipital. 0. C. 1338 A c. 



D. 631. The brain of a Guinea Baboon (Papio sphinx). The 

 two cerebral hemispheres have been detached. 



This specimen affords two more interesting variations in 

 the ever-changing area around the parieto-occipital sulcus. 



In a superficial view of the mesial aspect of the right 

 hemisphere there appears to be a Y-shaped combination of 

 parieto-occipital and calcarine elements. If, however, tin- 

 lips of the sulci be drawn asunder, the parieto-occipital is 

 found to be separated from the calcarine sulcus by a narrow, 

 deeply -submerged gyrus; and the apparent parieto-oceipital 

 sulcus consists of two distinct sulci, which are seen as such 

 on the left hemisphere widely separated by a broad gyrus. 

 On the right side, however, the two sulci are separated by 

 a submerged gyrus, and, after comparison with the last 

 specimen, there can be no doubt that the anterior sulcus 

 (that which appears to join the calcarine) corresponds to 

 the element hitherto called " parieto-occipital," whereas 

 the deeper and more extensive posterior sulcus (compare 

 the left hemisphere) is unquestionably identical with that 

 distinguished as the " ramus parieto-occipitalis sulci intra- 

 parietalis." But the importance of this specimen depends 

 upon the fact that upon the right hemisphere ilu- latter 

 sulcus is separated from the intraparietal sulcus by a small, 

 exposed, arcuate gyrus, which can be no other than that 

 called arcus occipitalis in Human Anatomy. Essentially 

 the same condition is found on the left hemisphere, but 

 the arcus occipitalis is submerged. 





