THE PITUITARY 343 



stalk of the pituitary). He considers that the structure is 

 not homologous with the " succus vasculosus " of fishes, as 

 Retzius thought. 



A very rare abnormality which has been described in con- 

 nection with the sphenoid bone is a persistent, perforating 

 foramen in the basisphenoid the canalis craniopharyngeus. 

 This is regarded as the place of exit of the original duct of 

 the anterior lobe of the pituitary body. 



Haberfeld finds the canal wanting in all acromegalic skulls 

 in the Vienna Pathological Institute. He reports that it is 

 very variable in individuals of the same species of animals. 

 He calls attention to the fact that the pharyngeal pituitary 

 is constant in man, while it is frequently absent in the lower 

 animals. This is not what would be expected if the structure 

 really represents the remains of the original duct of the 

 pituitary. 



2. The Pituitary Body of Birds and Lower Vertebrates 



In birds the epithelial cleft appears to be absent. The 

 cells of the anterior lobe are for the most part small and finely 

 granular. 



The posterior lobe is small and hollow, and much con- 

 voluted. Colloid bodies are sometimes present. The cells 

 of the pars intermedia come into -close contact with the nervous 

 portion of the posterior lobe, but are gathered together for 

 the most part in the neighbourhood of its neck and on the 

 thin lamina of nervous tissue forming the floor of the third 

 ventricle. 



In Teleostean fishes the posterior lobe has a complex vascular 

 structure of a glandular nature, which was called the ' ' saccus 

 vasculosus " by Gottsche. 



The Teleostean pituitary is composed of three kinds of 

 tissue, two of which are epithelial and the third nervous, 

 the latter being comparatively small in amount. The anterior 

 lobe of mammals is represented by a wedge-shaped mass of 

 large and deeply staining cells. These cells vary in situation 

 and extent in different species. The pars intermedia consists 

 of small, round, feebly staining cells, which surround and 

 invade the nervous tissue. The pars intermedia in the cod 

 is divided into two main portions, which are continuous 



