THE CEREBELLUM. 



1089 



directed forward and somewhat inward and, therefore, slightly oblique to the sagittal 

 plane. Anteriorly the nucleus reaches the level of a frontal plane passing through 

 the precentral fissure ; laterally it extends to about the middle of the hemisphere 

 (Ziehen) ; whilst medially its postero-inferior end comes into such close relation with 

 the fourth ventricle that a slight elevation, eminentia nuclei dentati, is produced on 

 the lateral ventricular wall. In its longest (antero-posterior) dimension the nucleus 

 measures from 15-20 mm., and in breadth about half as much. 



Of the other paired internal collections of gray matter the nucleus fastigii, the 

 nucleus emboliformis and the nucleus globosus the nucleus fastigii, or the roof 

 nucleus, is the best defined. It lies within the core of the worm, in the lower part 

 of the corpus trapezoideum, very close to the mid-line and to its fellow of the oppo- 

 site side. In its general form the nucleus is egg-shaped, with the posterior pole 

 somewhat prolonged, and in its sagittal diameter measures about 10 mm. and in the 

 transverse dimension about half as much. The nucleus extends from the base of the 



Nucleus fastigii 

 Nucleus globosus 



Rest i form body 

 (external division) 



Superior worm 



Decussation of 

 roof-nuclei 



Fourth ventricle 



Nucleus dentatus 



Restiform body 

 (internal division) 



Ventral 

 cochlear nucleus 



Flocculus 



Posterior longitudinal fasciculus 

 Pyramidal tracts 



Vestibular nerve 



Inferior olivary nucleus 



Section across upper part of fourth ventricle, showing internal cerebellar nuclei ; new-born child. 

 Weigert-Pal staining. Preparation by Professor Spiller. 



lingula to the stem of the pyramid, and in frontal sections (Fig. 942) appears circu- 

 lar in outline and closely related with fibre-tracts that in part end in the nucleus of 

 the opposite side. 



The nucleus emboliformis, or embolus, is an irregular wedge-shaped plate 

 of gray matter that partly closes the hilum of the dentate nucleus, in much the same 

 manner that the median accessory olivary nucleus obstructs the mouth of the chief 

 olivary nucleus. In its sagittal diameter it measures about 15 mm. , and in the vertical 

 one approximately one-fourth as much ; it decreases in thickness from about 3 mm. 

 in front to a slender wedge behind. The embolus rests upon the superior cerebellar 

 peduncle, its front end extending to within a few millimeters of the precentral 

 fissure and its posterior pole reaching almost as far back as the dentate nucleus, 

 with which it is united by a limited connection. 



The nucleus globosus lies close to the medial side of the embolus, between 

 the latter and the roof nuclei. In its general form the nucleus is comparable to a 

 sphere attached to a sagittally directed stalk (Ziehen). The globular head, about 

 5 mm. in diameter and somewhat transversely compressed, lies above the tonsil and 

 is continuous with the stalk that extends backward for a distance of about 8 mm. 



By means of uncertain and limited attachments the nucleus globosus is loosely 

 connected with the roof nucleus and the embolus, and also joins the postero-inferior 



