Nuclei Tuberis Laterales and the Ganglion Opticum Basale. 17 



ganglion are somewhat larger (the smallest cell illustrated in Pig. 38 

 shows only a small portion of a cell in optical section), the nuclear 

 membrane is not so definite, and the nucleus is larger. In macacus 

 (Figs. 44 and 49) the difference in distribution of the Nissl substance 

 is less than in any of the other animals, but even here the Nissl sub- 

 stance in the cells of the l>asal optic ganglion is more nearly confined 

 to the periphery, is denser here and not so dense in the interior portion 

 of the cell as in the case of the other cell group; this results in a 

 sharper differentiation between peripheral and central portions of the 

 cell in the case of the ba&al optic ganglion. Other differences in 

 macacus are: the cells and cell nuclei of the basal optic ganglion are 

 smaller than those of the nucleus paraventricularis (the opposite is 

 true in man), and the cells of this latter nucleus are rather piriform. 

 In the lemur (Figs. 50 and 54) the difference in distribution of the 

 Nissl substance is marked, the differentiation of the cell into peripheral 

 and central portions being much sharper in the cells of the basal optic 

 ganglion. In the cat (Figs. 55 and 58) the difference between per- 

 iphery and center of the cell is again more marked in the cells of the 

 basal optic ganglion, since in the cells of the other group the central 

 portion of the cell (including the cell nucleus) stains deeply (Fig. 58). 

 Note also in the cat that, just as in man, the cells of the basal optic 

 ganglion are larger, but unlike those of man have smaller cell nuclei 

 than the cells of the nucleus paraventricularis. 



The resemblance of the cell type in the case of the basal optic gang- 

 lion and the nucleus paraventricularis hypothalami is therefore very 

 close, but in all four animals studied the cells of the basal optic gang- 

 lion were found to be more sharply differentiated into a peripheral zone 

 containing dense masses of Nissl substance and an inner portion rela- 

 tively free from this substance, whereas in the cells of the nucleus par- 

 aventricularis hypothalami the Nissl substance was not so sharply 

 differentiated as to its distribution. It will be recalled that within the 

 cells of the nucleus tubero-mammillaris this differentiation was even 

 less marked than within those of the nucleus paraventricularis. 



Another cell group must be distinguished from the basal optic gang- 

 lion. This is the nucleus ansae peduncularis of Meynert (ganglion 

 basale of Kolliker) . It occurs in man, macacus and the lemur, but I 

 was unable to find it in any of my three series of the cat. Its location 

 and extent may be seen in the different illustrations. In all three 

 animals in which it occurs it is readily distinguished from the basal 



