SENSE OF TASTE. 735 



its edge near the tip, so as to affect not the substance of the organ, but 

 merely the papilla?, a taste sometimes acid, sometimes saline, like the taste 

 produced bv electricity, will be distinctly perceived. The sensation of taste 

 thus induced will sometimes continue several seconds after the application 

 of the mechanical stimulus." On the other hand, as Wagner has truly re- 

 marked, if the surface of the tongue near the root be touched with a clean 

 dry glass rod, or a drop of distilled water be placed upon it, a slightly bit- 

 terish sensation is produced ; and this, if the pressure be continued, passes 

 into that of nausea, and if the pressure be increased, even excites vomiting. 

 The feeling of nausea may be excited by mechanical irritation of any part 

 of the surface of the fauces or soft palate; and this feeling is certainly 

 much more allied to that of taste than to that of touch. Further, it has 

 been observed by Heule, that if a small current of air be directed upon the 

 tongue, it gives rise to a cool saline taste like that of saltpetre. Thus we 

 find that the peculiar effects of sapid substances upon the nerves of taste 

 may be imitated to a certain extent by other agencies ; and it also appears 

 that the sensations excited by these vary according to the part of the gusta- 

 tive surface on which they operate ; mechanical or electrical stimulation of 

 the front of the tongue giving rise to a kind of saline taste, whilst mechani- 

 cal stimulation applied to the back of the tongue and fauces excites the 

 feelings of bitterness and nausea. One of the conditions requisite for the 

 due exercise of the gustative sense, is a temperature not departing far on 

 either side from that which is natural to the body. It appears from the ex- 

 periments of Prof. E. H. Weber, 1 that if the tongue be kept immersed for 

 nearly a minute in water of about 125, the taste of sugar brought in con- 

 tact with it, either in powder or solution, is no longer perceived ; the sense 

 of touch, usually so delicate at the tip of the tongue, being also rendered 

 imperfect. A similar imperfection of taste and touch was produced by im- 

 mersing the tongue for the same length of time in a mixture of water and 

 broken ice. 



601. The surface of the Tongue is undoubtedly the special seat of gusta- 

 tive sensibility in Man ; though the sense of Taste is not by any means re- 

 stricted to that organ, being diffused in a less degree over the soft palate, 

 the arches of the palate, and the fauces. It is on the tongue alone, however, 

 that the papillary apparatus is fully developed ; and its structure has been 

 so carefully examined and described by Messrs. Todd and Bowman,' 2 that 

 little remains to be added to their account of it. The lingual papillae may 

 be divided, in the first place, into the Simple and the Compound, the former 

 of which had previously escaped observation, through not forming any ap- 

 parent projection. The Simple papilla? are scattered in the intervals of the 

 compound, over the general surface of the tongue ; and they occupy much 

 of the surface behind the circumvallate variety, where no compound papilla? 

 exist. They are completely buried and concealed beneath the continuous 

 sheet of epithelium, and can only be detected when this membrane has been 

 removed by maceration ; they are then found to have the general characters 

 of the cutaneous papilla?. The Compound papilla? are visible to the naked 

 eye; and have been classified, according to their shape, into the circumvallate, 

 the fung if or m, and the filiform. The circumvallate or calyciform papilla? are 

 eight or ten in number, and are situated in a V-shaped line at the base of 

 the tongue. Each consists of a central flattened circular projection of the 

 mucous membrane, surrounded by a tumid ring of about the same elevation, 



1 Miiller's Archiv, 1847, s. 342. 



2 Physiological Anatomy and Physiology of Man, vol. i, chap. xv. 



