The Lower Portion of the Hutiuui Bratii-Ston. 61 



cephalic border. After an oblique caudal slope, the border turns straight 

 ventrally for some distance along- the edge of the prominent upper cei)halic 

 lobe, which is well seen on ventral view (figvu'e 5). This border ends abruptly 

 in a right angle at the level of the secondary transverse gyrus of the dorsal 

 cephalic lobe. From this i)oint the border of the hilum continues caudally 

 in three great curves. The first of these curves, convex dorsally, ends at 

 the level of the first main transverse fissure on the dorsal surface. The 

 border is thence continued in the second curve, convex ventrally, to the 

 level of the second main transverse dorsal fissure. The third curve, arising 

 at this point and showing its convexity ventrally, continues around to the 

 dorsal border, forming in its course the rounded caudal limit of the hilum. 

 The main line of the dorsal border of the hilum is straight, but it is broken 

 by the notches made at the origin of the second and third transverse fissures 

 on the dorsal side (figure 7). 



The interior of the olive shows convolutions and sulci, which are in 

 every case merely the rcver.se of the sulci and gyri described on the oi:)posite 

 surfaces. The caudal end is formed by the caudal dorsal lobe and the third 

 lateral lobes, while the cephalic cap is composed wholly of the cephalic lobe. 



The olive is, then, a "hollow shell with a wrinkled wall." The lobes 

 described on the various surfaces merge into one another so that they may 

 be considered as a cephalic lobe, occurring on all the surfaces; a second 

 dorsal lobe, small and only on the dorsal surface; a third dorsal lobe, extend- 

 ing from the dorsal border of the hilum around all the surfaces; a lateral 

 lobe, arising as the dorsal lateral lobe, forming the middle lobe on the lateral 

 surface and continuing over to the center of radiation; and the small caudal 

 lobe. Hence, we may add that the olivary nuclear mass is composed of 

 these five easily distinguished lobes, some of which extend around the whole 

 leaf, while others are small and limited in extent. The three main trans- 

 verse dorsal fissures exist in the adult as in the new-born (Sabin), but there 

 is in addition a definite cephalo-caudal fissure which continues, in the charac- 

 teristic caudal obliquity, the lateral projection of the second transverse 

 furrow. These sulci are continued to the point of radiation on the ventral 

 surface, either directly or by a shallow, ill-defined grooving. 



The description given above is that of the left inferior olivary nucleus. 

 The right olive was likewise modeled, but with the purpose of showing its 

 relation to the formatio reticularis and to the other nuclear masses (figure 1, 

 cf. two sides). As it can not be removed from its position, an accurate 

 comparison with the left can not be made. However, it may be said that 

 although some slight differences may be made out, even as it lies in the model, 

 the same main fissures and furrows exist as in the left. There is the same 

 characteristic ventral radiation of furrows, the same distribution of lobes 

 on the lateral and ventral surfaces, with consequent agreement of all essential 

 morphological elements. 



