[Illustration: Fig. 25.--Taste-buds of rabbit. i., section across part of the pleated patch (enlarged); ii., taste-buds further enlarged.] This sense is generally localized in or near the mouth; in us mainly in the tongue. One manner, but not the only manner, in which the nerves in this region terminate is in the minute flask-shaped taste-buds, which have near one end, where they reach the surface, a funnel-shaped opening, the taste-pore. They are made up of elongated cells, some of which near the centre are spindle-shaped, and are called taste-cells. They are found chiefly round the large circumvallate papillæ; but in the rabbit and some other animals they are collected in the folds of a little ridged or pleated patch--the _papilla foliata_--on each side of the tongue near the cheek-teeth. It is probable that the stimulation of the end-organs of taste is effected by the special mode of molecular vibration due to the chemical nature of the sapid substance. Mr. J. B. Haycroft, in a paper read before the Royal Society of Edinburgh,[EO] suggests that "a group of salts of similar chemical properties have their molecules in a similar vibrating condition, giving rise to similar colours and similar tastes." "Thus the chlorides and sulphates of a series of similar elements--called a group of elements by Mendeljeff--have similar tastes." The delicacy of the sense of taste in man has been the subject of investigation by Messrs. E. H. S. Bailey and E. L. Nichols.[EP] They give the following table:-- I. Quinine-- Male observers detected 1 part in 390,000 parts of water. Female " " 1 " 456,000 " " II. Cane-sugar-- Male observers " 1 " 199 " " Female " " 1 " 204 " " III. Sulphuric acid-- Male observers " 1 " 2,080 " " Female " " 1 " 3,280 " " IV. Bicarbonate of sodium-- Male observers " 1 " 98 " " Female " " 1 " 126 " " V. Common salt-- Male observers " 1 " 2,240 " " Female " " 1 " 1,980 " " The above figures represent means or averages of a great number of individuals. There was very considerable variation for some tastes. In the case of the bitter of quinine, the maximum delicacy was the detection of 1 part in 5,120,000 parts of water; the minimum 1 part in 456,000 parts of water. Except in the case of salt, the sense was more delicate in women than in men. It is not stated whether the men tested were smokers. It does not seem necessary to say anything concerning the sense of taste in the lower mammalia.