116 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



length of the aqueduct of Sylvius, and is composed of large 

 multipolar ganglion-cells. In this nucleus we observe a certain 

 tendency in the cells to become separated into groups. One 

 collection of cells lying dorsad of the rest is plainly distinguish- 



able. 



While all the other oculo-motor fibres emerge from the 



side on which they originate, the fibres from this group of cells, 

 as was first shown by Gudden, pass in a median direction and 



decussate with those from the corre- 

 sponding group on the opposite side 

 Besides this dorsal group a median 

 group can be distinguished, just in 

 the middle line, which gives off 

 fibres on each side. 



Fig. 67 represents, partly in 

 diagram, the nuclei in the floor of 

 the aqueduct and their relations to 

 the nerve-roots. You will notice in 

 the cut two small nuclei situated 

 one on each side of the median line, 

 and connected with each other ante- 

 riorly and below. They are marked 

 a and b. These two nuclei, which 

 were first observed by myself in fcetal 

 brains, and later by Westphal, dur- 

 ing a painstaking examination of the 

 .aqueduct of syi : adult brain, lie in a thick net-work 

 of nerve-fibres. It is not yet known 

 whether they stand in any relation 

 to the oculo-motor, and, if they do, what the relation is. We 

 possess such an array of clinical facts and discoveries made by 

 careful post-mortem dissections that we may venture to desig- 

 nate the particular spot in the nucleus which supplies each 

 individual ocular muscle. 



I will give you Starr's table, the latest result of these 

 researches which were so happily begun by Kahler. According 



(Partly diagrammatic.) 



