54 A Reconstruction of the Nuclear Masses in 



gradually into the lateral surface except in the cephalic portions, but it is 

 rather sharply distinguished from the lateral surface. The dorsal surface 

 is fairly straight, whereas the lateral surface shows a marked general con- 

 vexity. On the ventral surface, the lower two-thirds are mainly flat, but 

 the upper one-third exhibits a slope toward the dorsal surface. The mesial 

 surface includes the hilum of the nuclear body and shows the invaginations 

 of the convolutions of the dorsal surface. 



The convolutions of the olive resemble, in general, those of the cerebral 

 cortex as pointed out by Dr. Sabin. However, there is a very striking 

 difference between the principal and secondary sulci here in the olive, a far 

 more marked distinction than exists over the cerebral cortex. Generally, 

 as in the new-born, the main furrows on the dorsal surface run transversely, 

 but on the lateral surface this direction is converted into an oblique one, 

 the sulci coursing somewhat laterally but chiefly ventrally and caudally 

 (figure 2). The ventral surface shows the radial distribution of sulci as 

 pointed out by Miss Sabin (figures 1 and 5). 



Three principal sulci, corresponding to those in the medulla of the new- 

 born, are distinguished on the dorsal surface of the inferior olive (figure 7). 

 In the main, these are deejicr and run more closely to the l)order of the 

 hilum than do the other secondary furrows. These sulci tlivide the dorsal 

 surface into four lobes a cephalic lobe, occupying nearly one-third of the 

 whole dorsal leaf; two middle lobes (the second and third lobes of Sabin), 

 and the small caudal lobe. The first fissure, that between the cephalic and 

 the second lobes, is the most poorly differentiated of the main sulci (figure 

 7, a). Its importance, however, is assured by its broad character and the 

 general straight course which it follows, unaffected by the secondary sulci 

 which enter it. This first fissure begins just lateral to the border of the 

 hilum, courses out in a direct transverse line to almost the lateral limit of 

 the dorsal surface, and then dips laterally, caudall}^ and \-entrally as the 

 main oblique fissure on the lateral surface of the olive (figures 5 and 7, a). 

 The transverse dorsal portion of this main fissure is bisected by a very deep 

 furrow, arising just cei)halad to this first fissure a fourth ])riiicii)al fissure. 

 This deej) furrow bisecting the transverse is continued caudally as the deepest 

 fissure of this surface, forming the lateral margins of the second fissure and 

 of the middle lobes. This deep fissure runs almost exactly cephalo-caudally 

 with but slight lateral deviation in its caudal portion. Becoming more 

 shallow about the middle of the third lobe, it curves ovor ui)on the lateral 

 surface, to form the inferior limit of the middle lateral lobe. The second 

 chief transverse fissure of the dorsal surface arises from the dorsal edge of 

 the hilum at approximately its middle point and courses transversely to 

 the deep cephalo-caudal fissure (figure 7, 6). Its direction is transverse for 

 three-fifths of its length and then becomes caudally inclined, to fuse with the 

 cephalo-caudal fissure at an angle of 45. This second pi'incipal sulcus is 

 the deepest uf the fissures of the olive. The thin! or caudal principal sulcus 



