9a FREDERICK TILNEY 
its definite relations to the pars tuberalis, and appears with but 
slight variations in the same general conformation as described 
in the cat. The most considerable modifications in its form 
are seen in the anthropoids and man. In these forms it does 
not hold the same relation to the floor of the interbrain as in 
the lower mammals. This change is occasioned by the forward 
and downward rotation which occurs in the hypophysis as the 
latter sinks into the deepened sella turcica. Another factor 
operative in this change is the foreshortening of the sella in man 
and the apes which further tends to force the pituitary gland 
craniad. The rotation from the developmental standpoint 
seems to be secondary to the increased depth in the pituitary 
fossa, for in the five-month human fetus, as the writer has 
previously shown (8), the post-chiasmatic eminence occupies 
a position corresponding in all details to that of the adult cat. 
It is only in the late fetal and early post-natal stages that the 
protuberance undergoes a change in relations which in effect 
_is the result of a rotation of the hypophysis through 90°. When 
this is completed the surface described in the cat and other 
mammals as ventral no longer presents a ventral inclination 
but is turned craniad, while the eminence as a whole has become 
elongated in its long axis and constricted transversely. As a 
result it has a more or less bulbous appearance, a fact which has 
given rise to the term bulbus infundibult. 
The most caudal structures entering into the floor of the third 
ventricle are the corpora mammillaria (27); the one on the left 
side is shown in figure 2. In the adult cat these bodies are large 
protuberances situated one on either side of the median line and 
immediately cephalad to the posterior perforated space. They 
appear in all the mammals studied and are also present though 
less conspicuous in sauropsid forms. 
The post-infundibular eminence (34) occupies a_ position 
immediately in front of the mammillary bodies. In lateral 
view (fig. 2) it does not appear so prominent as the latter struc- 
tures nor has it the sharp lateral demarcation of the corpora. 
On the other hand, it is definite in all mammals. So far as may 
be stated upon the evidence of the material examined it is most 
