398 



THE EXTERNAL CONFIGURATION 



Hemisphere, instead of being much less, is about equal to, 

 or it may be of even slightly greater bulk than, the con- 

 joined Fronto- Parietal segment. Thus the proportions 

 met with in the lower human types are, as it were, in- 

 termediate between those 

 which obtain in the higher 

 human types on the one 

 hand and in the Quadru- 

 mana on the other. 



The diminution in size 

 of the Tempore- Occipital 

 segment in the brain of 

 human beings generally, is 

 perhaps more apparent than 

 real. The very great in- 

 crease in the size of the 

 Frontal and of the Parietal 

 regions is, at least in part, 

 another means of accounting 

 for the altered proportion. 

 It is certain, indeed, that 

 the convolutions of the Tem- 

 poral Lobes tend to become 

 more complex in higher 

 human brains, and it is 

 equally certain that there 

 is also a tendency to an 

 actual increase in the size 

 of the Occipital Lobes. In 

 the more highly evolved 

 brains these Lobes become 

 deeper and also fuller and 

 more rounded. There is, moreover, a notable increase in 

 the complexity of the Occipital Convolutions. 



Fig. 145.— Undet buif.i c of Ctrel>ral 

 Peduncle, Pons, and Medulla, showing 

 Connections of the Cranial Nerves. (Sap- 

 pey, after Hirsclifeld.) 



1, Infundibiilum of pituitary body ; 

 2, part of floor of third ventricle ; 3, cor- 

 pora mamillaria; 4, cerebral peduncles; 

 5, j)ons ; C, optic nerves, crossiug- in the 

 middle line so as to form the ehiasma ; 



7, common motor nerves of e.\eball; 



8, nerviis patheticus ; 9, trigeminus ; 

 10, external ocular nerve ; 11, facial nerve; 

 12, auditory nerve ; 13, nerve of Wrisberg ; 

 14, glossopharyngeal nerve; 15, A'agus or 

 pneimiogastric ; 16, spinal accessory ; 

 17, hypoghssal nerve (cut av^^ay on one 

 side). 



