Abstract
This study is based upon 5 dogs with a lesion in the subthalamic region, in which the subthalamic nucleus of Luys was particularly involved. Two lesions were made with a probe, the remaining 3 by the injection of a very weak solution of silver nitrate. The animals were allowed to live from 8 to 11 days, and their symptoms observed. The brains were then prepared by the Marchi method for degenerated nerve fibers.
A large fasciculus of very fine rather diffusely scattered fibers leave the subthalamic nucleus on its medial side, the ventral part of the fasciculus being embedded in the cerebral peduncle. These fibers then run caudad as a wide band over the dorsal and medial surface of the substantia nigra and are distributed as follows:
(a) About half of these subthalamic fibers terminate in a nucleus of large, rather closely packed cells occupying an area in the form of an inverted comma. The broad, somewhat rounded head of this nucleus is located between the medial side of the substantia nigra and the mammillary peduncle. From this head a wedge-shaped group of cells extends laterally over the dorsal surface of the substantia nigra. This group of cells begins caudal to the mammillary bodies and extends beyond the upper level of the red nucleus.
(b) Many of the fibers from the subthalamic nucleus of LUYS pass more medial and terminate in a field of more scattered cells near the midline, dorsal and medial to the mammillary peduncle, and within the tegrnentum ventral and medial to the red nucleus. This field of cells begins just cephalad to the red nucleus and continue almost to its caudal level.
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