PITUITARY GLAND. 
1175 
A. D., and after his time far into the middle ages, even 
if the conception was modified in several manners, the 
cerebral hypophysis was explained as an extremely im- 
portant organ for the purification of the fluids contained 
in the brain. It was also called the gland for the se- 
cretion of the nasal mucus ( glandula pituitaria), an error 
which was not refuted until the seventeenth century. 
Another opinion was advanced, which even at the be- 
ginning of the present century was maintained by so 
eminent an anatomist as Meckel, namely that it secreted 
some kind of important fluid, which was supplied to 
foetal life than afterwards and is comparatively larger in 
young persons than in old, as is the case with several 
other organs whose significance appears to be more 
historical than physiologically clear. 
Better than its function, however, we know the 
origin of the hypophysis". In man it arises as an in- 
volution of the embryonic ectoderm in the region which 
afterwards becomes the roof of the mouth cavity. This 
involution rises, towards the anterior end of the noto- 
chord. It makes its appearance before the mouth ca- 
vity proper is formed, and long before the mouth has 
Fig. 346. Longitudinal section of the forepart of larvse of Petromyzon Planeri , after A. Dohkn. A three days, B six days, C seventeen 
days after exclusion. 
Ch, chorda dorsalis; Ent, entoderm; Ep , epiphysis; Hy , hypophysis; Inf , infundibulum; M, stomodreum, future mouth cavity; Max , upper 
jaw; Mdb, lower jaw; MT, mouth tentacle; N, nasal sinus, future nasal cavity; Thy, thyreoid gland; Tub. cin, tuber cinereum. 
the third ventricle of the brain. In modern days phy- 
siology does not seem to devote very much attention to 
its interpretation; it is most generally referred to the 
so-called blood-vascular glands, which it resembles in 
the greater part of its structure. Remarkable is the 
circumstance that it has a more robust growth during 
broken a passage through the pharynx to join the in- 
testinal canal. In the form of a tube it grows up to- 
wards the rudiment of the brain; and when the floor 
of the skull is developed the lower part of this tube 
closes, in the region where the presphenoid bone sub- 
sequently coalesces with the postsphenoid; the coinmu- 
“ The first investigator hereof was Rathke, Ueber die Entstehung der Glandula pituitaria , Mullers Archiv 1838, p. 482. 
Scandinavian Fishes. 
148 
