146 Herrinoj 



neck of tlie posterior lobe of a kitten in which the two layers are shown, 

 surrounded by the epithelial columns of the intermediate portion of the 

 pituitary. 



The distinction between the two layers begins at the junction between 

 body and neck of the posterior lobe, and is continued throughout the 

 laminae which connect it to the brain. In mesial sagittal section the ap- 

 pearances of a Cajal preparation are very striking. The finely granular, clear 

 outer layer extends anteriorly to the tuber cinereum, increasing in size as it 

 passes forward. The inner layer of longitudinally running fibres diminishes 

 in thickness, but is quite well marked where it fuses with fibres and cells 

 of the tuber cinereum. In the posterior lamina the two layers are eijually 

 distinct, but the longitudinal fibres are fewer in number, and both layers 



Fig. 13. — Mesial sagitt:il section through anterior lamina of nervous 

 substance in floor of third ventricle of adult cat. Drawing from 

 a section prepared by Cox's modification of Golgi's method. 



a, ependyma cells ; 6, inner layer of horizontal fibres ; c, outer layer of vertical 

 fibres from ependyma cells; d, position of cells of pars intermedia of tongue-like 

 process. Cf. flg. 8. 



become very thin towards their junction with the brain substance in the 

 region of the corpora mamillaria. The cells which line the cavity and 

 neck of the infundibulum vary somewhat in appearance, according to the 

 methods of fixation and staining employed. In the kitten, as revealed by 

 Cajal's method, there may be more than one layer of rounded cells from 

 which, as in fig. 12, fibres arise. None of the cells are ciliated in the cat. 

 In the adult there is one layer of cells, but others often lie among the fibres, 

 and appear to give origin to some of the latter. The anterior lamina in 

 front of the neck of the infundibulum is lined by cells, which, when 

 prepared by Golgi's method, have the appearance shown in fig. 13. Thej^ 

 are well-developed ependyma cells, and their branching processes pass 

 outwards, giving rise to the vertical striation which in Cajal and other 

 preparations is characteristic of the outer layer of the neck of the infuijdi- 

 bulum. In Golgi preparations these cells appear to give off" processes which 



