46 A Reconstruction of the Nuclear Masses in 



it goes cephalad and this portion of the nucleus l^ecomes a thin sheet of 

 cells, overlying the fiber bundle which separates it from the dorso-lateral 

 plate. The surface is irregular, from the occurrence of small prominences 

 upon it. On its most cephalic portion in this model it shows several ventral 

 projections which overlie mesially the lateral pontine wall (figure 14). 

 Between the mesial eminence on this side and the rectangular column of 

 large cells (mesencephalic root) is a marked ridge lying just ventral to the 

 ventro-lateral angle of the fourth ventricle. It begins caudally as a small 

 column of cells in the indifferent gray matter at the angle of the ventricle 

 and continues cephalad to the limit of the model (figure 14). Its cephalic 

 course, in the extent of the model, is somewhat dorsal and mesial. The 

 mass expands as it goes cephalad into a mesial elevated ridge which becomes 

 greater in the mesial and dorsal projections. Soon after it arises caudally, 

 it is well marked off from the mesial cell-mass of the nucleus, but its dorsal 

 limit is not well defined until after the triangular plate, ventral to the 

 dorso-lateral roof plate, has joined with it. Histologically the mass is well 

 differentiated. 



NUCLEUS INTERCALATUS. 



With its caudal extremity at the dorsal angle of the nucleus nervi 

 hypoglossi and with its cephalic termination just cephalic to the inferior 

 limit of the- nucleus nervi abducentis, the nucleus intercalatus of Staderini 

 and Von Gchuchtcn extends superficially beneath the floor of the ventricle, 

 underlying the area plumiformis (figure 3). The nucleus measures in its 

 cephalo-caudal axis 8.3 millimeters and its greatest transverse diameter 

 measures 2.3 millimeters. Corresponding measurements given by Streeter 

 are 11 millimeters and 2.0 millimeters. Hence, in the medulla sectioned by 

 Streeter the nucleus was longer and perhaps narrower than in the medulla 

 used for this reconstruction. 



Dorsally, the nucleus intercalatus is covered solely by superficial neu- 

 roglia and by the ependyma of the ventricle, except in its cephalic portion 

 where the stria? medullares course across it. The caudal two-fifths of the 

 nucleus lie mesially in relation to the dorso-lateral surface of the nucleus 

 nervi hypoglossi and laterally to the nucleus ala? cinerea?. The mesial 

 relations of the cej)halic three-fifths of the nucleus are with the nucleus 

 funiculi teretis and with the raphe; the lateral relations of this portion of 

 the nucleus are with the nucleus nervi vestibularis medialis and with the 

 nucleus nervi abducentis in the most superior part. Ventrally, the nucleus 

 is covered by the formatio reticularis. Such, then, are the relations of the 

 nucleus intercalatus to the adjoining masses of nuclear material. 



The dorsal view of the nucleus intercalatus (figure 3) and the mesial 

 view (figure 4) show the general morphology to be that of a diamond, or of 

 two cones with their bases approximated. The point of maximum diameter 

 occurs at about the junction of the caudal two-fifths with the cephalic 



