14 .1 h'cconatruvtion of the Nuclear Ma.sses In 



As soon as this appears, the enlargement shows a cupping for the caudal 

 pole of the inferior olive and the formatio reticularis recedes from it to form 

 a ventral surface at some distance posterior to the dorsal leaf of the olive. 

 This ventral surface is smooth in the main, with a slight curvature, so that 

 it faces for the most part mcsially as well as ventrally. The nucleus olivaris 

 accessorius dorsalis lies central to it, separated by a small series of fiber 

 bundles. The mesial edge of this surface is very irregular in its upper two- 

 thirds, while its lower one-third is in intimate relation with the dorsal margin 

 of the nucleus olivaris accessorius medialis. Alcove the superior mesial angle 

 of the dorsal accessory olive is an irregular ventral spur. The lateral bor- 

 der of this ventral surface of the formatio reticularis in the olivary region 

 shows a gentle concavity which includes the olive. It is continued laterally 

 into a roughened ventro-lateral plate which exhibits a very irregular dorsal 

 border, projecting laterally over the lateral surface of the main mass of 

 gray matter. 



The mesial surface of this olivary portion, bordering laterally the stratum 

 interolivare, is fairly smooth, showing many gentle eminences. 



At the superior end of the inferior olivary nucleus the lateral wall is 

 marked by the masses of gray matter projecting out from the vestibular 

 nucleus along the entering vestibular nerve. This surface is continued 

 upward into a mass of gray matter l.ying dorsal to the vestibular nuclei 

 the dorsal projections of the medial and superior portion (figure 13). On 

 dorsal view (figure 3) these masses are shown cut off abrujitly on the right 

 side of the model. Continuing cephalad, the j^rojections are seen to merge 

 into the dorso-lateral plates of the superior vestibular and of the trigeminal 

 nuclei. 



The extreme lateral surface above the vestibular complex is marked 

 by the irregular bulbous swelling of the sensory portion of the trigeminal 

 nucleus. A'entral to this the wall is continued irregularly into the dorsally 

 projecting lateral wall of the j^ons. The mesial surface of this portion of the 

 general gray matter is smooth and approximates the line of the raphe, as 

 the median fillet assumes the transverse direction and divides the pontine 

 nuclei from the formatio reticularis. 



The ventral surface of the formatio reticularis, in the region ce])halic 

 to the sui)erior pole of the nucleus olivaris inferior, shows a very striking 

 ventral projection. This is seen in part in figure 13. As the superior pole 

 of the olive recedes and vanishes, the formatio reticularis sends ventrally a 

 long, narrow, mesial spur and a shorter lateral spur (figure 13) ; these arc 

 well defined and arc^ separated by longitudinall}^ coursing fillers. These 

 projections surround somewhat and join with the cells of the pontine nuclei. 

 The mesial of the two masses does not extend cephalad for a very great 

 distance, as it is abi-uptly eliminated by the changing of the medial lemniscus 

 to its tran.sverse jjosition in the cephalic portion of tiie pons. The shorter, 

 thicker, lateral projection continues to carry the formatio reticularis tissue 



