Nuclei Tuberis Laterales and the Ganglion Opticum Basale. 21 



the two fissures referred to previously, the lateral (just medial to the 

 pes pedunculi) does not occur, since the obliquity of the plane of section 

 is such that it appears only in sections situated further caudally. The 

 medial one of these two fissures, however, appears in every section from 

 Figs. 11 to 15, and as in the other series, forms superficially the medial 

 boundary of by far the greater portion of the nuclei tuberis laterales. 



MACACUS RHESUS. 



In macacus the location of the nuclei tuberis laterales is similar to 

 that in man, except that in most sections only one cell group is shown, 

 and the cell mass does not invade the medio-ventral portion of the 

 tuber. A comparison of Figs. 19 to 22 (macacus) with Figs. 1 to 8 

 (man) will show that in both animals the nuclei differ but little as to 

 location. The two parallel furrows on the base of the brain are shown 

 in Figs. 19 and 20. 



In both man and macacus the nuclei tuberis laterales have, accord- 

 ingly, practically the same location, and by far the greater portion is 

 situated in the previously described region; this region, bounded ven- 

 trally by the two parallel furrows, laterally by the pes pedunculi, and 

 dorsally by the fornix column, is occupied caudally by the nucleus 

 tubero-mammillaris, and the nuclei tuberis laterales displace this 

 nucleus as one passes orally, and after the optic tract has fused with 

 the tuber, the nuclei tuberis are continued orally in the angle between 

 the pes pedunculi and the optic tract. Since the purpose of this paper 

 is in part to give a foundation for experimental study, it should be 

 noted that the main cell mas^ of fue nuclei tuberis laterales may be 

 accurately loaded in the intact brain just beneath the surface of the 

 most lateral portion of the tuber cinereum, between the two parallel 

 furrows and just caudal (medial) to the optic tract. In toluidin blue 

 sections the nuclei may be distinguished as circumscribed, lightly 

 staining areas by means of the unaided eye. As previously stated no 

 trace of the nuclei tuberis laterales is present in the cat, while in the 

 lemur they are indicated so faintly that it seems best not to attempt to 

 represent them in the illustrations. 



Separation of the nuclei tuberis laterales from surrounding cell groups 

 through differences in cell character. 

 The nuclei tuberis laterales are readily distinguished from the sur- 

 rounding cell groups not only in that they are sharply circumscribed 

 cell masses having a constant location, but also through their charac- 



