A CASE OF CYCLOPIA 217 



nucleus of the lateral lemniscus {Nu.l.l.) is also apparent. The 

 striae acusticae (s.a.) are but poorly medullated. 



The glossopharyngeus and vagus nerves (N.IX and X) to- 

 gether with the tractus solitarius (T.s.), nucleus alae cinereae 

 (Nu.a.c.) and nucleus ambiguus {Nu.amb.), are shown in figures 

 27 to 32. 



The accessory nerve (N.XI) shows a somewhat anomalous 

 condition of development. But few fibers of its medullary por- 

 tion could be distinguished ©n the left side. On the right, these 

 fibers are grouped peripherally in a compact bundle which is 

 well shown in figure 24, lying just within the ventral border of 

 the substantia gelatinosa (s.g.). These fibers apparently take 

 their origin from the central gray matter lateral to the central 

 canal. No definite nucleus could be distinguished in this, region 

 but these fibers are clearly not related to the nucleus ambiguue; 

 vide Cajal (3). 



The hypoglossal nerve (N.XII) and its nucleus (Nu.N.XII) 

 are normal in their relations. There is no sharp line of demar- 

 cation between the hypoglossal nucleus and the motor nuclei of 

 the anterior horn in the upper cervical cord. The accessory 

 nucleus of Roller is also to be made out. 



Arcuate nuclei (Nu.a., figs. 25 to 34). These bodies are prom- 

 inent in the lower medulla and are here somewhat larger than 

 normal. On the appearance of the inferior olive, however, they 

 diminish in size and at the level of the pons become continuous 

 through the nucleus of the raphe with the nuclei pontis. 



Inferior olive (Nu.o.i., figs. 27 to 35). These form very promi- 

 nent projections on the ventral aspect of the medulla. They are 

 somewhat larger than normal. . As the series in this region was 

 not absolutely complete, the exact antero-posterior diameter 

 could not be determined but it would not be much less than 

 8 mm. The greatest dorso-ventral diameter is 5.6 mm and the 

 transverse diameter is 3.8 mm. These dimensions in Sabin's 

 model (20) were 7.5 mm., 4.48 mm., and 6.5 mm., respectively. 

 There has been, therefore, an increase of the dorso-ventral at 

 the expense of the transverse diameter. This change of form is 

 probably due to the absence of the pyramids. In transverse 



