CHAP, v.] TASTE AND SMELL. 255 



always soaked in moisture, whereas the epidermis of the skin is as 

 a rule dry. 



The dermis, thrown up into numerous conspicuous papillae, 

 contains a considerable quantity of reticular, or at places, even 

 adenoid tissue, is extremely vascular, plexiform arrangements of the 

 veins being very frequent, and in it in many situations, for instance 

 in the tongue, striated muscular fibres end with branched ter- 

 minations ; numerous small chiefly albuminous glands are also 

 present, especially in certain regions. 



In the tongue, the papillse, which are for the most part com- 

 pound, have been divided into three classes ; filiform, fungiform, 

 and circumvallate. The two first, which are much the most 

 numerous, differ chiefly in form, the one being more or less 

 pointed, the other having a broad head ; both generally bear 

 secondary papillse. The circumvallate papillae, few in number, 

 arranged in the form of a V with the apex at the root of the 

 tongue, are distinguished by the fact that the papilla is as it 

 were sunk into the substance of the tongue, so that its base is 

 surrounded by a circular groove like a fort surrounded by its fossa 

 and vallum. 



863. Appearing irregularly and scantily on the fungiform 

 papillse and then seated sometimes at the sides, sometimes on the 

 top of the papilla, more abundant on the circumvallate papillae, 

 in which they are seated generally on the sides of the papilla, 

 looking into the groove, but sometimes on the opposite wall or 

 vallum, are the structures known as taste-buds or "taste-bulbs." 

 These are especially abundant and most easily studied in the aggre- 

 gations of papillae, which in some animals, for instance the rabbit, 

 are found at the back of the tongue and are called papillae foliatoe. 

 In the rabbit these are seen by the naked eye as two oval 

 patches, one on each side, placed obliquely at the root of the 

 tongue. Upon examination each patch is found to consist of a 

 number, twenty or so, of folds of the mucous membrane placed 

 side by side like the leaves of a book. In each fold the dermis is 

 raised up into three narrow parallel ridges which in a transverse 

 section appear as three pointed papillae. The epithelium, which 

 here as elsewhere consists of a malpighian and a corneous layer, 

 is somewhat thin at the sides of the fold, but thicker at the 

 top, where it is even, not following in contour the ridges of the 

 dermis beneath. Hence, in each fold, the two outside ridges of 

 the dermis, which look towards the deep narrow furrows sepa- 

 rating each fold from adjacent folds, are covered by a somewhat 

 thin but complete epithelium. And in a transverse section this 

 epithelium is seen to contain a vertical row of oval structures, four 

 or five in number, which reach from the dermis to the surface of 

 the epithelium, each furrow having a row of such structures on 

 each side. These are the taste-buds, having essentially the same 

 structure as those seen in man less regularly distributed on 



