58 A Reconstruction of the Nuclear Masses in 



olive with the raphe in the cephahc part. Three lobes may be distinguished 

 on the lateral surface, the lateral continuations of the cephalic, lateral, and 

 third dorsal lobes. The main fissures separating these lobes can be made 

 out in their depths only when the olive is viewed from the inferior side as 

 the cephalic lobe overlies dorsally and laterally the first transverse sulcus 

 (a), while the lateral dorsal lobe similarly obscures the lateral projection of 

 the dorsal cephalo-caudal fissure. 



All the fissures seen on the lateral view have a marked obliquity caudally 

 and ventrally (from above downwards and forwards) in the upper two-thirds 

 of this olivary mass (figure 2). In the lower one-third the sulci run trans- 

 versely and then curve ventrally and cephalad. Xo secondarj' sulci at right 

 angles to the main furrows are made out on this surface, the secondary sulci 

 all being long and shallow, paralleling the direction of the main grooves. 

 The first main lateral fissure, a continuation of the first main dorsal furrow 

 (a), is concealed by the overlying gyrus of the lateral cephalic lobe for a 

 portion of its course. About the middle of the lateral surface the furrow 

 becomes superficial and may be traced ventrally and caudally to its ending 

 (figure 5, a). Just before its termination at the junction of the lateral and 

 ventral surfaces the .sulcus bonds abruptly cei)halad and ventrally. Sui)crior 

 to this main furrow is a rather long parallel groove which reall}^ follows the 

 line of the secondary transverse sulcus of the dorsal cephalic lobe, although 

 interrupted by a small gj'rus. Sujierior to this sulcus are several parallel 

 grooves, which divide this lateral cejihalic lobe into many obliquely coursing 

 gyri. Taken as a whole, the lateral cephalic lobe comi;)rising one-half of 

 this surface ma.y be considered as made up of three main convolutions, all 

 of which follow the course of a ventral and caudal projection. 



The middle lateral lobe (figure 2) is likewise composed of three chief 

 convolutions, separated by well-marked sulci. The first groove, encountered 

 as on(! goes caudally from the lateral obliquity of the first transverse dorsal 

 sulcus (a), is a parallel and deep sulcus which arises from the lateral end of 

 the transverse furrow and runs caudally, laterally, and ventrally to terminate 

 in the first lateral sulcus as it bends cephalad. The small gyrus, thus 

 delimited by these two obliriue grooves, is concealed in its superior half ])y 

 the overhanging caudal gyrus of the lateral cephalic lobe. The inferior 

 part of this gyrus is readily seen from the lateral surface. Caudal to this 

 gyrus is the first main convolution of the middle lateral lobe a projecting, 

 flat, l)road gyrus which curves olilicjucly caudalwards, lateralwards, and 

 then ventralwards and cephalad. Shallow, broad, and somewhat indistinct 

 grooves mark its surface. It is bounded below by a fissure which is con- 

 cealed on this view , tlic oblique sulcus of the lateral dorsal lobe. Caudally 

 are placed the other two convolutions of this lobe, separated by a shallow 

 crescentic fiUTow. The middle {'on\'olutioii projects laterally more than do 

 the other gyri, while the lower lobe is distiiiguislied l)y a caudal projection 



