172 Proceedings of Royal Society of Edinburgh. [sess. 
of tlie two postero-lateral nuclei will pass through the dorsal ex- 
tremity of the median nucleus. The upper portion of the median 
nucleus is hounded laterally by fine medullated fibres wdiich arise 
from its nerve cells and pass along its outer surface forwards to 
enter, partly, the root of the nerve, and partly the posterior longi- 
tudinal fasciculus. It is also connected with the adjacent portions 
of the anterior group by a fine network of medullated fibres. The 
lower part of the median nucleus (fig. 4) has an irregularly circular 
outline. It has no lateral boundary of nerve fibres. 
D. The postero-internal or pale nucleus (figs. 5, 6, 7, 9, p.i.n.) 
presents in sections of the adult brain which have been stained by 
Weigert’s hsematoxylin a remarkably pale appearance. It is 
wedged in between the median and postero-external nuclei (see fig. 
5, p.i.n.), but extends to a higher level than the former. It ter- 
minates above by a large club-shaped head (fig. 9, fig. 7). (This 
apparently corresponds to the medial nucleus of Westphal.) Its 
pallor is due to the comparative absence of medullated fibres 
between, and the large lymph spaces which surround, the nerve 
cells contained in it. These cells differ from those of the other 
group, being more oval or rounded, containing large spherical nuclei 
having fewer processes, and staining of a much fainter brown by 
Weigert’s method. 
E. The superior (or small-celled nucleus of Darkschewitsch) lies 
at the extreme upper extremity of the oculomotor nucleus, forming 
a small indefinitely circumscribed group at the outer margin of the 
posterior longitudinal bundle. It deserves a special name from its 
distinct segmentation from the postero-lateral group and from the 
small size of its cells. It is imbedded among the fibres of the outer 
portion of the posterior longitudinal fasciculus, many of the fibres 
of w T hich evidently terminate in its cells, and it forms the terminus 
of many of the fibres of the posterior commissure. 
Roots of the Third Nerve . — The sections tend to confirm at least 
partially the statements of Kahler and Pick as to the origins of the 
nerve. The roots of the postero-lateral and external group of nuclei 
form the most external fibres of the nerve as it passes through the 
tegmentum. They constitute, however, the upper as well as the 
lower external fibres. The anterior nucleus sends its roots into the 
innermost part of the nerve, while fibres from the median and the 
