130 Herring- 



The posterior lamina, after leaving the neck of the infundibuluni, is sharply 

 bent back upon itself, and appears in sagittal section as a long thin strip of 

 brain substance tapering as it passes backwards until it joins the septum 

 between the corpora niamillaria. The bend in the lamina encloses 

 epithelium which is continuous with the epithelial investment of the 

 posterior lobe, and which has in the cat a distinctly tubular character in 

 this situation. In coronal section the opening of the neck into the third 

 ventricle is not so wade, and the lateral laminae are shorter. The neck is 

 really funnel-shaped, but compressed from side to side. It is completely 

 invested by epithelium. 



In the dog the anterior lobe almost completely embraces the posterior, 

 but the main mass of the lobe containing eosinophil cells lies below it and 

 at its sides. Prolongations of the anterior lobe pass over the dorsal aspect 

 of the posterior lobe to unite with one another. The epithelium is reflected 

 at the neck, and at the postero-superior extremity of the posterior lobe, to 

 form an investment which covers the nervous portion of the lobe. The 

 reflected portion of the epithelium is separated from the outer covering by 

 the cleft, which is extremely well developed in the dog's pituitary. Finger- 

 like processes of the epithelium which invests the posterior lobe frequently 

 project into the cleft, and sometimes join with the outer layers of epithelium, 

 forming strands across it. The cleft is a closed cavity in the dog, but the 

 epithelium bounding it is very thin at the posterior reflection, and conse- 

 quently liable to rupture there in course of preparation. 



The investment of the posterior lobe is thick, and portions of it pass 

 deeply into the nervous substance. It contains no eosinophil cells, but 

 numerous colloid vesicles. The vesicles are larger in the dog than in the 

 cat, and occur in groups which are for the most part situated in the deeper 

 layers of the epithelium, and are not infrequently found in the adjacent 

 nervous substance. 



The pituitary body of the monkey (fig. 5) presents a very different type. 

 The posterior lobe is solid and the cavity of the third ventricle is not even 

 prolonged into its neck. The attachment of the pituitary to the brain is 

 by a narrow solid stalk of nervous substance, which is surrounded by a 

 thin layer of epithelium continuous with the anterior lobe. 



The anterior lobe lies in front of the posterior, and is partly separated 

 from it by the cleft. The main mass of the anterior lobe lies in front of 

 the cleft, and is made up of columns of cells, many of which stain deeply 

 wath eosin, and of blood -channels. The epithelial investment of the 

 posterior lobe is moderately thick behind the cleft, and contains no 

 eosinophil cells. It is continued round the posterior lobe and completely 

 invests the neck, spreading on to the adjacent parts of the brain, but is 

 usually deficient tow^ards the middle line on the posterior aspect of the 

 nervous lobe. The main blood-vessels enter and leave the posterior lobe 

 in this situation, and in all animals examined the epithelial investment 

 stops more or less short of this place. The epithelium frequently dips 



