860 



TASTE. 



susceptible than the lingual to gustative im- 

 pressions, far less readily excites manifesta- 

 tions of pain when subjected to mechanical 

 irritation. Hence, it would seem not im- 

 probable, that there may be in each a mixture 

 of the fibres which minister to the sense of 

 taste with those of tactile sensibility ; and 

 that the former may be so far special in their 

 endowments, as to be capable of receiving 

 only the peculiar impressions made by sapid 

 bodies, to which the latter may be insensible. 

 Such a view would seem to be supported by 

 the cases of Vogt and Noble just referred to ; 

 and it is in harmony with the views to which 

 we are led from the consideration of the 

 diversities manifested between the sense of 

 heat and cold and that of simple contact. [See 

 TOUCH.] 



Gustative Papilla;. The tongue is copiously 

 furnished with a papillary structure, bearing 

 a close resemblance to that of the skin, but 

 in many respects more complicated. Re- 

 ferring to the article TONGUE for a more par- 

 ticular anatomical description of these papilla?, 

 we have now to inquire into their connexion 

 with the sense of taste. According to the 

 recent investigations of Messrs. Todd and 

 Bowman, the lingual papillae are either simple 

 or compound ; the former, which do not differ 

 from those of the cutaneous surface in any 

 other obvious character than the nature of 

 their epithelial investment, are scattered over 

 the whole surface of the tongue, in parts where 

 the others do not exist, but they also par- 

 ticipate in the formation of the compound 

 papilla? ; the latter are of three kinds, the cir- 

 cumvallate or cali/ciform, t\\efiingifun, and the 

 conical. The drcumvallate papilla?, \\hich are 

 only eight or ten in number, and are restricted 

 to a small space at the base of the tongue, 

 consist merely of groups of simple papilla?, 

 arranged in a peculiar manner, and separated 

 from those of the adjacent mucous membrane 

 by a circular fissure. Into these simple papillae 

 it has not yet been found possible to trace 

 any distinct nerve-fibres, though there can be 

 little doubt that it is penetrated by at least 

 the essential part of them. The fuiigiform 

 papilla? are scattered singly over the surface, 

 chiefly about the sides and apex, and but very 

 sparingly in the middle of the dorsal region, 

 though they are abundant in front of the cir- 

 cumvallate papilla?. These are composed of 

 aggregations of simple papillas, which rise, 

 however, considerably above the surface, and 

 are covered with an epithelium so thin that 

 they are distinguished by their blood-red 

 colour. Fasciculi of nerve-tubes may be dis- 

 tinctly traced into them ; but of the nature 

 of their termination it would be unwise to 

 give a positive statement. Some of the ap- 

 pearances presented by them favour the idea 

 that they form loops at their peripheral ex- 

 tremities ; whilst, in other instances, the tu- 

 bular portion of the fibre, with the white 

 substance of Schwann, seems to terminate 

 somewhat abruptly, whilst the central axis is 

 continued onwards into the substance of the 

 enveloping t'ssue, in which it loses itself. 



The conical or filiform, which are the most 

 numerous of the compound papillae, are dif- 

 fused over the whole surface of the tongue, 

 though most largely and numerously de- 

 veloped in its central part. They consist of 

 clusters of simple papilla? of a peculiarly 

 elongated form, containing tubular nerve- 

 fibres, which may frequently be seen to form 

 distinct loops in their interior ; but their chief 

 peculiarity consists in their epithelial invest- 

 ment, which forms about two-thirds of their 

 length, and gives to them their whitish tint. 

 This investment consists of a tuft of long 

 pointed processes, some of which present a 

 near approach in their dense texture to hair ; 

 whilst others may be regarded as soft or un- 

 condensed hairs. These processes are sent off 

 from the sides and summits of the secondary 

 papilla?, and are usually inclined backwards, 

 lying buried in the recesses of the mouth. 

 The foregoing description applies, however, 

 only to the conical papilla? of the human 

 tongue ; and there is a considerable diversity 

 in their structure in other animals. Thus, in 

 the Ruminants, each conical papilla is ter- 

 minated by a long, slender, flexible, horny 

 filament, curving backwards ; and in the Fe- 

 lines some of them are furnished with a brush- 

 like tuft of slender horny filaments, like those 

 of man*, whilst others are encased by firm 

 horny sheaths, which are prolonged backwards 

 as stiff spines. It is to this arrangement that 

 the peculiar roughness of the tongue of the 

 cat is due ; the organ being thus enabled to 

 act as a flexible rasp, whereby the bones 

 which they lick may be effectually cleaned of 

 the smallest particles of flesh that may adhere 

 to them ; and a single stroke of the tongue of 

 a lion is said to be capable of abrading the 

 whole thickness of the human skin. 



After what has been already said of the 

 conditions essential to the exercise of the 

 sense of taste, there is no occasion to do 

 more than point out the evident fact, that, if 

 some of the papilla? be covered with an epi- 

 thelial investment so dense as to resemble 

 horn, and offering an effectual barrier to the 

 penetration of fluids, these cannot be sup- 

 posed to have much participation in the 

 sense, if they possess any. It is obvious that 

 in the Felines the function of the spiny pa- 

 pilla? must be purely mechanical ; and it 

 seems probable that the brush-like papilla? 

 which lie among them, in common with those of 

 man, possess simple tactile sensibility, serving 

 to direct those muscular actions of the organ, 

 which so remarkably adapt it to deal with 

 minute particles of food. On the other hand, 

 the thinness of the epithelial investment on the 

 simple papilla? which are scattered over the 

 surface of the tongue, and which form the 

 circumvallate and fungiform papillae by their 

 aggregation, indicates their special adaptation 

 to receive gustative impressions ; and this must 

 be admitted to be more especially the case 

 with the fungiform papillye, which often 



* By Cuvier these filaments are supposed to be 

 the ultimate fasciculi of the fibres of the gustalive 

 nerve ; but this is certainly an error. 



