481 
[Tuckerman. 
fortunately, little could be learned of their structural details. The 
best marked bulb was spheroidal in shape, and in some respects 
resembled those of the soft palate and epiglottis. It measured 
0.030 mm. in length and 0.027 mm. in breadth, and was placed 
vertically in the long axis of the papilla, with its lower two-thirds 
resting in a cavity of the mucosa. The outer extremity of the 
bulb penetrated the superficial layers of the epithelium. While 
embryonic taste-bulbs were wanting in the tongue of a ten weeks 
embryo, it is not improbable that they may yet be found in the in- 
cipient stages of growth in one of the twelfth week of intrauterine 
life. 
The same observer has also found bulbs in the human foetus at 
the fourth month, the middle of the fifth, and at later periods of 
intrauterine life. They always make their appearance first at the 
upper part of the papilla, that is on the exposed surface. The more 
advanced among them being epithelial in position, while the less 
mature are largely embedded in the stroma of the mucosa. By the 
sixth month of foetal life, bulbs begin to appear on the lateral 
area of the papilla, but they are much less advanced than those 
of its free surface. In the new-born child, and until the fourth 
month of life, isolated bulbs may still be found on the free area of 
the papilla ; at a later period they occur but rarely there. 
What purpose the temporary taste-bulbs (for such they seem 
to be) of the free upper surface of the circumvallate papillae sub- 
serve in the embryo is difficult to comprehend. With the appear- 
ance of the bulbs of the lateral area they gradually disappear, and, 
from all indications, perish. By the time the bulbs of the free 
surface of the papillae have attained their full development, bulbs 
in early stages of formation make their appearance on the wall, 
the lowermost bulbs being the most elementary. Were it other- 
wise it might be conceivable, as Hermann suggests, that by an 
unfolding of the papilla laterally the bulbs of the free area are 
shifted to the sides. In the present state of our knowledge, there 
seems to be no better way than to believe with Hoffmann, that 
“ the bulbs of the free surface perish through the proliferation of 
the ordinary epithelium.” It is not improbable that, after the bulbs 
have once disappeared from the upper surface, certain altered con- 
ditions of the epithelium prevent, save in rare instances, their re- 
currence there. 
PROCEEDINGS B. S. N. H. VOL. XXIV. 31 MAT, 1890. 
