The circumvallate group comprise the largest and the most important papillæ. There are only from eight to twelve or sixteen of this type, and by their arrangement they form the V-shaped figure on the superior surface of the tongue, mentioned above, and which divides the anterior two-thirds from the posterior third of the tongue. These papillæ are found nowhere else. They rise only slightly above the surface of the tongue from the bottom of a pit or cup-shaped depression, giving the impression of a small mound surrounded by a ditch, whence the name, circumvallate. In a few cases more than one papilla rises from a single pit, but in most cases there is but one. The papilla itself has an average height of 2 millimeters, with a diameter at the top of 1.0 to 1.5 millimeters, and slightly less at the base. The cup-shaped depression averages about 1 to 1.5 millimeters in depth. The largest of these papillæ is that one forming the apex of the V-shaped figure and is called the foramen cæcum. The smallest are those found at the ends of the V. The fungiform papillæ are so called on account of their resemblance to a toadstool. Each consists of a rather slender stalk capped by a relatively large, rounded head, about .8 to 1.0 millimeter in diameter. The whole papilla has an average height ranging from 1.0 to 1.5 millimeters. These are scattered very irregularly over the superior surface of the tongue, most of them being found on its anterior two-thirds. However, a few are found back of the circumvallate papillæ, but always very close to them. They are most numerous on the sides and the tip of the tongue, where they appear as bright red points upon the paler background of the tongue covering. The total number of this type has been estimated at from 150 to 200. The third type, the filiform papillæ, cover the whole superior surface of the tongue and are so numerous that no estimation of their total number has been made. They are arranged in fairly regular lines running to each side from the middle line of the tongue and parallel to the lines formed by the circumvallate papillæ. They are believed to contain no sensory ends of taste and have only a mechanical function, if any, in connection with the taste mechanism. They are conical or cylindrical in form and vary in height from 1.5 to 2.5 millimeters. Sometimes these papillæ are covered with tiny secondary papillæ, which, however, are not apparent to the unaided eye. The foliate papillæ consist of numerous small folds of the membranous covering of the tongue upon its sides and just in front of the line formed by the circumvallate papillæ. In these folds a large number of the taste bodies are imbedded. In certain animals, especially the rodents, these foliate papillæ form a very prominent part of the tongue, while in man they are no more prominent than the other forms.