Nuclei Tuheris Laterales and the Ganglion Opticum Basal e. 15 



questions as to the elementary mechanisms of the nervous system. In 

 the case of the basal optic ganglion, therefore, I shall not be content 

 with having pointed out its location and extent, but shall proceed to 

 compare the character of its cells with that of the cells of surrounding 

 groups ; such a comparison serves not only to set aside this cell group 

 as different from other cell groups by virtue of differences in cell 

 character, but it enables us also to recognize certain similarities of cell 

 character between the cells of the ganglion and the cells of other groups, 

 so that different degrees of relationship between the different cell 

 groups may be provisionally stated. 



I shall first point out the differences in cell character between the 

 cells of the basal optic ganglion and those of the surrounding groups 

 so .as to complete the picture of this cell group ; afterwards the relations 

 of various cell groups will be discussed (but not until the nuclei 

 tuberis have been described). There is no diiSculty in distinguishing 

 the cells of the basal optic ganglion from those of the nuclei tuberis 

 and of the substantia grisea ventriculi tertii. This is shown by a 

 reference to the corresponding figures 38, 39 and -iO; 4-1, 45 and 46; 50 

 and 51; 55 and 56; moreover the difference between the cells of the 

 basal optic ganglion and those of the substantia grisea is well shown in 

 Fig. 37. 



The cells of the basal optic ganglion may be readily distinguished 

 also from those of the nucleus tubero-mammillaris, although both types 

 of cells have a certain similarity; the failure to recognize the unity of 

 the cell complex known as the nucleus tubero-mammillaris (mammillo- 

 infundibularis) and to clearly separate it from the basal optic ganglion 

 is one of the most important causes for our meager knowledge of this 

 region. Considering first the relations of these tvi'o cell groups as to 

 location, it is evident from the illustrations that they are closely related 

 only for a short distance. Moreover the cells of the nucleus tubero- 

 jnammillaris are for the most part rather diffusely scattered, while 

 those of the basal optic ganglion are densely packed together and the 

 cell group is further characterized by the intercellular feltwork formed 

 by the coarse colorless cell processes ; these two points may be observed 

 by comparing Figs. 36 and 37. Comparing the cell type of the two cell 

 groups the fundamental difference found in all four animals involves 

 the appearance of the Nissl substance ; in both forms the Nissl substance 

 is located principally on the periphery of the cell, but in the cells of the 

 basal optic ganglion the massing of the Nissl substance on the periphery 



2 



