126 Herring 



enclosing a cavity which is a continuation of the third ventricle. The 

 infundibulum has a funnel-shaped origin from the base of the brain, 

 narrowing as it passes backwards to a tubular neck, then expanding to 

 form a hollow club-shaped body which makes up the larger portion of 

 the posterior lobe. The central cavity also enlarges behind the neck 

 of the infundibulum. 



The anterior lobe, composed of epithelial cells, lies below, and its thickest 

 portion is in front of the infundibulum. It extends for some distance 

 anteriorly, forming a tongue-shaped projection which reaches to the under 

 surface of the tuber cinereum. The anterior lobe also spreads further 

 laterally, and enfolds the sides of the infundibulum, the neck of which 

 is encircled completely, so that, as in the figure, a portion of the anterior 

 lobe appears above it. In some kittens the wrapping of the epithelium 

 round the posterior lobe is more complete, and the only part of the lobe 

 which is never covered by epithelium is a small part behind where the 

 blood-vessels make their entrance. A narrow and somewhat S-shaped 

 space lies inside the epithelium close to and following in its outline the 

 under surface of the nervous portion of the posterior lobe, but separated 

 from it by several layers of epithelium. The space or cleft is, as Kolliker 

 (20) pointed out, the remnant of the cavity of the pouch of buccal 

 epithelium from which the anterior lobe is derived. The layer of epi- 

 thelium which lies between the cleft and the part of the posterior lobe 

 developed from the brain is comparatively thin, and very closely applied 

 to the nervous substance, thus forming an investment to it which is more 

 or less complete according to the degree in which the anterior lobe has 

 grown round the posterior. The cleft extends laterally, and in some cases 

 almost surrounds the body of the posterior lobe. The posterior lobe as 

 separated from the anterior by the cleft is therefore a composite body 

 derived from the brain and from buccal epithelium, and it is to this 

 structure of elements derived from two sources that the name of posterior 

 lobe is usually applied, although strictly speaking the epithelial investment 

 belongs developmentally to the anterior lobe. The cleft is sometimes 

 more complicated, and branches of it may run into the substance of the 

 anterior lobe. Serial sections show no opening below such as has been 

 described by B. Haller (14), nor does there appear to be an opening at 

 any point ; the cleft is a closed cavity in the kitten, but very great care 

 has to be taken in the removal and preparation of the pituitary to prevent 

 rupture of the thin layer of epithelium which is continued backwards 

 from the anterior lobe. 



The greater portion of the anterior lobe is a solid structure made up of 

 columns of cells and wide blood-channels. Granules are present in many 

 of the cells of this part, but are not so marked a feature of the anterior 

 lobe in the new-born kitten as they are in the adult cat. Colloid cysts are 

 not found in the pituitary of the new-born kitten. 



The relation of the pituitary body to the sella turcica is shown in fig. 1. 



