UNILATERAL CEREBELLAR AGENESIA 389 
Fig. 17 Transverse section through the isthmus at the emergence of the 
fourth nerve. Weigert-Pal. 33, left central tegmental tract; 34, medial 
lemniscus; 42; right superior cerebellar peduncle; 43, right mesencephalic tri- 
geminal root; 44, left superior cerebellar peduncle; 45, left lateral lemniscus: 
46, right lateral lemniscus; 47, left mesencephalic trigeminal root; 48, right 
central tegmental tract; 49, abnormal fibers in left central gray. 
