48 .4 Reconstruction of the Nuclear Musses in 



abrujitly laterally at the caudal end of the nucleus of the round bundle and 

 then gradually cephalad to the cejihalic pole of the nucleus intercalatus. 

 The borders of the U[iper three-fifths of the nucleus intercalatus are fairly 

 straight and gradually converge, to form an abrupt cephalic pole, mesial 

 and slightly cephalic to the caudal extremity of the nucleus nervi abducentis 

 (figure 3). 



The relative dorso-ventral and transverse diameters of the upper cone 

 of the nucleus and of the region of greatest thickness may be made out by 

 comparison of the dorsal and mesial views (figures 3 and 4). The two 

 diameters in these portions of the nucleus intercalatus are approximately 

 equal. Below the area of greatest dimensions, the dorso-ventral diameter 

 remains })ractically constant, while the transverse diameter diminishes rapidly 

 as one passes caudally. 



NUCLEUS TRACTUS SOLITARII. 



In this reconstruction of the adult medulla, the nucleus lying lateral 

 to the fibers of the tractus solitarius was modeled. Melius (1903) described 

 this nucleus in the medulla of the dog and identified a similar chain of cells 

 lying lateral to the tractus in the human medulla. It was considered that 

 this cell-column probably more truly rei)rcsented the nucleus of the solitary 

 bundle than do the irregular and ill-defined cell-groups situated mesially to 

 the tractus, between it and the nucleus alse cinereae. The dorso-mesial cell- 

 mass has been included by several authors as an integral part of the nucleus 

 of the solitary bundle; one portion of this dorso-mesial cell-collection has 

 been described in the subdivision of this study dealing with the nucleus ahe 

 cinerese. 



The caudal end of this continuous chain of cells lateral to the tractus 

 solitarius lies at a slightly higher level than does the caudal enil of the nucleus 

 ate cinerccC (figure 10). The nucleus ends above just caudal to tlie superior 

 termination of the nucleus ahe cinerese (figure 4). Its cephalo-caudal length 

 is 10.1 millimeters, just slightly less than that of the nucleus alse cinereae. 

 Along the mesial and dorso-mesial border of the nucleus runs the tractus 

 solitarius. Dorsal to the nucleus is the nucleus fasciculi gracilis in the caudal 

 half, while in the cephalic half the nucleus nervi vestibuli pars descendens 

 occupies this position (figure 11). Lateral to the nucleus is the nucleus 

 fasciculi cuneati and in the most cephalic portion the substantia gelatinosa. 

 Dorsal to the nucleus lies the nucleus alse cinerea?, while mesial to it lies the 

 nucleus nervi hy])Oglossi. Ventrally and laterally from the nucleus of the 

 tract is found tlie substantia gelatinosa. At no point is the nucleus at all 

 superficially placed as regards the floor of the ventricle. 



The nucleus begins below as an irregular column of cells, and runs from 

 tliis point ('(>phalad, somewhat ventrally and laterally. The caudal three- 

 fifths of the nucleus form an irregular cell-column, almost round on cross- 

 section and situated at some distance mesially to the curving ventro-mesial 



