20 Edward F. Malone. 



On examining Figs. 1 to 6 these two fissures are seen to be practically 

 parallel, and the area bounded by them and by the fornix column under- 

 goes as we pass orally the following change : in the caudal portion (Fig. 

 1 ) this area is occupied by the cells of the nucleus tubero-mammillaris, 

 whose caudal pole constitutes the lateral ganglion of the maniraillary 

 body; passing further orally these large cells are replaced (especially 

 those situated ventrally and medially) by the small cells of the nuclei 

 tuberis laterales and of the substantia grisea. Accordingly the oaudal 

 portion of this region is continuous with the lateral ganglion of the 

 mammillary body, whereas orally it gradually becomes the lateral 

 portion of the tuber cinereum. In this region included between these 

 two fissures ventrally, the pes pedunculi laterally, and the fornix 

 column dorsally, lies by far the greater portion of the cells of the nuclei 

 tuberis laterales. Referring to Figs. 1 to 8 the location and extent of 

 these cell groups are evident, and only a few comments will be necessary. 

 The nuclei tuberis laterales consist of a variable number of well circum- 

 scribed nests of small cells, and can be distinguished even without the 

 aid of their characteristic cell type. These different cell nests are 

 more or less connected with one another, and their separation is to be 

 regarded probably as dependent upon the mechanical influence of fiber 

 masses, since their partial fusion, identical cell type, -and variable 

 number would seem to exclude the possibility of these separate groups 

 having different functions. The cell nests of the nuclei tuberis later- 

 ales are practically free from cells of surrounding groups. 



In considering the second series of man (Series D, Figs. 11 to 15) it 

 is absolutely essential to understand the plane of sectionr; this has 

 already been described in considering the basal optic ganglion. It will 

 suffice to point out that Series D differs from Series AC in that the 

 plane of section of the former passes more caudally as it passes from 

 dorsal to ventral ; and that in it the opposite sides of the brain are cut 

 asymmetrically, in that the lateral portion of each section of Series D 

 is situated further oral than the medial portion of the corresponding 

 section. As was previously noted the plane of section of Scries D is the 

 only one which can pass through the right optic tract at right angles 

 to its long 'axis ; this relation to the optic tract will render a clear picture 

 of the plane of section relatively easy. Bearing this plane o^ section 

 in mind a study (with the aid of a hand lens) of Figs. 11 to 15 will 

 show that the location of the nuclei tuberis laterales in Series D is 

 practically the same as in the preceding Series AC, Figs. 1 to 8. Of 



