335 



Gustatory Structures. 



The Circumvallate Papillae. These papillae measure 

 about 0,80 mm in breadth and 0,45 mm in height, and are slightly de- 

 pressed below the level of the adjacent lingual area. They vary in 

 size and shape, and are more or less verrucose. The epithehum cov- 

 ering their upper surface measures in places 0,3 mm in thickness. 

 The trenches encircling them are neither very wide nor very deep, 

 but pass beneath the papillae in such a way as to give them a con- 

 siderable expanse of under surface. Serous glands are not very 

 plentiful. Their ducts open into the trench at its base and sides. 



The taste-bulbs of this region are arranged in four or five tiers, 

 each tier containing, on an average, about fifty bulbs. The bulbs are 

 most numerous in the lower tiers, the epithelium lining the expanse 

 of under surface of the papilla being quite filled with them. They 

 are fairly uniform in size and measure 0,06 mm in length and 0,032 mm 

 in breadth. The diameter of the gustatory pore is about 0,0033 mm. 

 Non-medullated nerve-fibres run to the bases of the bulbs, and can 

 also be followed, for a short distance, into the epithelium between 

 them. In many bulbs, the sensory cells may be seen protruding through 

 the taste-pore. 



The Papillae foliatae. Most of the folds composing these 

 papillae are marked by a central cleft of some depth. On each side 

 of the main cleft are several smaller ones, the number depending upon 

 the number of secondary papillae borne by the fold. The furrow 

 have a fairly uniform breadth, but their depth varies, averaging about 

 0,55 mm. Serous glands are relatively more abundant here than in 

 the circumvallate area, and their ducts open at the usual places. 

 Close by the foliate organs the ducts of the mucous glands open di- 

 rectly on the free lingual surface. Each papilla foliata possesses eight 

 bulb-bearing folds. Three or four smaller folds are usually present, 

 but they are destitute of bulbs and are unsupplied with serous glands 

 or ducts. The bulbs are disposed irregularly at the sides of the folds, 

 there being from five to nine tiers of them. They vary greatly in 

 width, some having a transverse diameter of 0,045 mm. The mean 

 breadth, however, is 0,035 mm, and the length 0,057 mm. The tiers 

 are rather short, not usually containing above eleven bulbs in their 

 entire length. Taste -bulbs occur but sparingly in the fungiform 

 papillae. 



