TYPES OF PYRAMIDAL DECUSSATIONS INTHE CHINESE BRAINS

Seventy-one pyramidal decussations of normal adult brains were observedin the present study, nine out of which together with a case of degeneration ofthe pyramidal system were examined microscopically. To these were added 9series of sections of adult brain stems and 11 series of new-born brain stems. Macroscopically, the pyramidal decussations in the Chinese brains fell into6 types: 1. no visible decussation; 2. unilateral single crossing; 3. bilateral singlecrossing; 4. interdigitating; 5. interlacing; and 6. mixed. Besides, in one casethe pyramidal decussation presented itself externally a rounded prominence. Macroscopic features were not in complete comformity with microscopic find-ings. Particularly at the two ends of the decussation, macroscopic obser-vation could not frequently be definite. Great variations were observed in the existence and magnitude of the ven-tral corticospinal tract. In the case of pyramidal degeneration, the direct ventrola-teral pyramidal tract was revealed.