10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



THE HYPOPHYSIS 



Owing to the small size of the alligator's brain, in proportion to the 

 size of the animal, the hypophysis is very small and is quite difficult 

 to remove, without injury, from the skull. Its position and size in 

 relation to the brain are shown in the outline figures 14 and 15 (pi. 3). 



Back of the optic chiasma the prominent infundibulum (in) is seen, 

 projecting caudad and ventrad and connecting, more intimately than 

 is indicated in figures 14 and 15', with the nervous portion (nl) of 

 the hypophysis. This nervous portion, to be described later, was 

 doubtless somewhat stretched in dissecting out the brain from which 

 the two figures under discussion were drawn ; its normal condition is 

 probably better indicated in the drawing of the sagittal section 

 (fig. 16, pi. 3). 



The main mass of the hypophysis is made up of the glandular lobe 

 (gl) from which the small middle loJDe cannot here be distinguished. 

 It is oval in outline, somewhat depressed, as shown in figure 15, and 

 projects caudad from the nervous region. 



A sagittal section through the infundibulum and hypophysis of an 

 alligator is shown in figure 16, the anterior region being, of course, 

 to the left. The infundibulum (in) has a deep cavity (V^) lined 

 with a distinct, darkly-stained ependyma (cp) somewhat thicker 

 towards the base of the cavity, that is, to the left. 



The nervous portion of the hypophysis (nl) is an irregular, lobu- 

 lated mass continuous caudad with the infundibulum. As seen in 

 this and the following figure its cavity (ch) has a complicated outline 

 and is continuous, of course, as is its ependyma (ep) with the third 

 ventricle (V^) and its ependyma. Its capsule (c) is seen in figure 17 

 (pi. 3) to send a long projection into the tissue of the lobe from the 

 ventral side. As mentioned above, this region of the hypophysis is 

 seen, in the sagittal section, to be less elongated than is shown in 

 figures 14 and 15. 



The middle part of the hypophysis (ml) as is seen in figures 16 

 and 17, is continuous with the caudad surface of the nervous lobe, 

 and, in fact, more or less surrounds it, especially on the dorsal and 

 ventral sides. It is somewhat broken up into larger and smaller areas 

 and is so closely continuous with the much larger glandular part that 

 the two regions cannot be distinguished from each other in surface 

 views, as has already been noticed. No cleft between the middle and 

 glandular portions is to be seen. 



The glandular part of the hypophysis (gl), as seen in sagittal section 

 (fig. 16), is a large, darkly-stained mass directly continuous, caudad, 



