278 F. Tuckerman — Gustatory Organs 



arranged in a triangle, the apex of the triangle being directed 

 backward toward the epiglottis. The foliate papillae are situ- 

 ated obliquely on each side of the back of the organ, anterior to 

 the glosso-palatine arch, their anterior extremity being directed 

 downward and inward. Each papilla is about 5 mm long and 

 2 - 7 mm broad. As seen from above, they are small, oval-shaped 

 elevations, and are marked transversely by a number of ridges 

 or lamellae with intervening furrows. 



Gustatory Structures. 



The circumvallate papillce. — The general surface in front 

 of these papillae is covered, as already mentioned, with small 

 conical papillae. The immediate area around them, however, 

 is nearly free from papillary elevations. When well developed 

 the circumvallate papillae measure O60 mm in diameter. Their 

 summits are circular or slightly oval, and are more or less 

 marked by verrucose elevations. Occasionally I have seen a 

 fungiform papilla superposed upon one of this type. Each 

 papilla is encircled by a narrow and rather shallow trench. 

 Serous glands are abundant within the papillae, and beneath 

 and around them. Their ducts, which are numerous, open into 

 the trench at its lower part. Mucous glands are also very 

 plentiful in this region of the tongue, and their ducts have a 

 greater diameter than those of the serous glands. They pass 

 through the mucous membrane and open, somewhat obliquely, 

 on the free lingual surface. In a horizontal section, two and 

 a half millimeters square, I counted eighty ducts. The mu- 

 cosa composing the body of the circumvallate papilla is cleft 

 into three main portions, the central portion or lamella being 

 much the largest, and overtopping the other two. In this 

 particular the papilla bears a structural resemblance to the 

 fold of the lateral organ, in which the mucosa is similarly ar- 

 ranged. The depressions between the lamellae not infrequently 

 extend to the base of the papilla, forming a deep and narrow 

 furrow; "usually, however, they are partially filled with epithe- 

 lium. Covering the mucosa is a thin layer (O03 mm in thickness) 

 of stratified pavement epithelium. This layer is thicker above 

 than at the sides, but the difference is only slight. 



The taste-bulbs of this gustatory area occupy a somewhat 

 exposed position. They are confined to the upper three fifths 

 of the papillary wall instead of filling its lower and conse- 

 quently more protected portion, as is the case in other Roden- 

 tia which I have investigated. They are also present in the 

 corresponding region of the outer wall of the trench. The 

 bulbs, to all appearance, are in contact by their edges and, in 

 the papilla, are disposed in a zone of four to six tiers. Those 

 embedded in the epithelium at the upper part of the outer 



