HISTOLOGY OF THE CENTRAL NERVOUS SYSTEM OF THE WEDDELL SEAL. 863 
a large anterior lobe, a narrow but well-defined intermediate part, and a posterior lobe ; 
the hinder portion of the intermediate mass is bent at an angle upon the rest of that 
part, so as to come to lie posteriorly between the lower limit of the posterior lobe 
and the projecting posterior part of the anterior lobe. From the surface, the upper 
part of the posterior lobe appears wedge-shaped and folded over the hinder part of 
the anterior lobe so as to cover about a third of the upper surface. 
The atypical tissue on the upper surface takes the form of a small ovoid mass 
folded upon itself, and the upper leaf appears to be continuous with the floor of the 
Sin. A323 
Wee WAR) kc JO 
AN SEAE ES 
— 
y 
BME 
ant.¢. 
Fic. 7.—A mesial sagittal section of the pituitary gland (Leptonychotes weddellii), (Semidiagrammatic. ) 
ant.l. Anterior lobe: A A, its front part ; | x. Hypothetical mass on the superior aspect of 
BB, its posterior part (see Plate II.). | the infundibulum. 
mid.t. Intermediate portion. sin. Sinusoids. 
post.t. Posterior lobe. col. Colloidal substance formed in the middle lobe. 
n. Neck of the infundibulum. b.v. Large blood-vessels in the posterior lobe (often 
op.t. Optic tract. filled with colloid), 
3rd ventricle; its structure, however, in no way resembles either grey or white 
matter, being made up of strands of conglomerate cells (syncytium) between which is 
a considerable amount of connective tissue and some relatively large vessels (text-figs. 
8 and 9). Below this body comes a layer continuous with the posterior lobe, then 
the persistent cleft continues with the third ventricle and passing some way into 
the “neck” of the posterior lobe, and below this again the lower part of the neck in 
which a small amount of the above atypical tissue also occurs, but, as will be seen, 
quite separate from the main mass. 
