Nuclei Tuberis Laterales and tJie Ganglion Opticum Basale. 27 



Conclusion. 



I have described with tlie aid of illustrations the location ^and extent 

 of the basal optic ganglion and nuclei tuberis laterales in four forms 

 of manxiuals, and have showii their relations to the surrounding cell 

 groups of the hypothalamus; moreover the cell types of these two cell 

 groups have been shown to differ radically, and the differences in cell 

 character have been pointed out through which one can readily and 

 accurately distinguish each of these two cell groups from those which 

 surround it. Accordingly the principal purpose of this study has been 

 accomplished, namely, to prepare a foundation of such a character as 

 to make further study possible. It is now possible to study in the same 

 manner neighboring portions of the telencephalon, or to e.vtend with 

 relative ease the present study of the hypothalamus through a much 

 longer phylogenetic series than the critical nature of this study has 

 permitted ; the relations of the various cell groups of the hypothalamus 

 can be studied also from the standpoint of histogenesis ; or the nature 

 of the cell processes and the character of the nerve endings around the 

 cells of each group may be determined. But the greatest use of this 

 study is that it makes possible intelligent experimental investigation 

 of the hypothalamus. Experimental workers have been inclined to 

 pass over differences in cell character and to make little or no attempt 

 to correlate cell function with cell character, and fail to clearly recognize 

 a fact to which I have, in a previous article, called attention in the 

 following words : " The histological character of a nerve cell is an indi- 

 cation of its function. Differences in connections with portions of the 

 organism which differ merely in spatial relations do not involve a 

 difference in the character of the nerve cells, but are associated merely 

 with the location of the nerve cell ; for instance, arm and leg muscles, 

 flexors and extensors are all innervated by the same tyix; of cell, 

 although such differences in peripheral connections correspond to the 

 differences in the position of the corresponding nerve cells." It is there- 

 fore evident that experimental work which detemiines the connections 

 of various portions of a given region with different portions of the 

 organism, without taking into consideration differences of cell character, 

 fails to distinguish between differences of connection dependent merely 

 upon spatial differences and those differences of connection which 

 involve differences in cell activity, such cell activity being indicated, 

 not only in the nervous system but in all portions of the entire organism. 



