174 THE AMERICAN MONTHLY [Oct. 



number of letters in each name ; that of Willis making 9, 

 and that of Sommering making 12,) or the name con- 

 taining the more letters has the larger number of pairs 

 of nerves, and vice versa). The cortex of the cere- 

 bellum is divided into three layers of cells, granular, 

 Purkinje's cells, a molecular layer. 



Each hemisphere is divided externally into tive lobes 

 of which four are visible, frontal, parietal, temporal, oc- 

 cipital and one invisible, insula (Isle of Reil). Roughly 

 speaking, the visible lobes correspond to the bones of the 

 cranium ; that is, the frontal lobe is underneatli the 

 frontal bone, the parietal lobe beneath the parietal bone, 

 etc. The brain contains five'Ventricles, of which four are 

 visible — the right and left, (1st and 2nd,) the 3d and the 

 4th ; and one invisible, the 5th or pseudo-ventricle. The 

 cortex of the brain contains 5 distinct layers of gang- 

 lion cells. 



Studying carefully 100 cases of brain tumor in which 

 an ophthalmoscopic examination had been made for the 

 presence or absence of choked disc (optic neuritis). Dr. 

 Krauss announced the following conclusions: 



Optic neuritisis present in about 90 per cent of all cases 

 of brain tumor. It is more often present in cerebral 

 than in cerebellar cases. The location of the tumor exerts 

 little influence over the appearance of the papillitis. The 

 size and nature of the tumor exerts but little influence 

 over the production of the papillitis. Tumors of slow 

 growth are less inclined to be accompanied with optic 

 neuritis than those of rapid growth. It is probable that 

 unilateral choked disc is indicative of disease in the hem- 

 isphere corresponding to the eye involved. It is doubtful 

 whether increased intracranial pressure is solely and 

 alone responsible for the production of an optic neuritis 

 in cases of brain tumor. 



