736 



OF THE ORGANS OF THE SENSES, AND THEIR FUNCTIONS. 



FIG. 253. 



Capillary plt-xus of 

 fungiforui papilla of the 

 Tougue. 



from which it is separated by a narrow circular fissure. The surface of both 

 centre and border is smooth, and is invested by scaly epithelium, which con- 

 ceals a multitude of simple papillte. The fungiform papillae, varying in 



number from 160 to 290, 1 are scattered singly over the 

 tongue, chiefly upon its sides and tip. They project 

 considerably from the surface, and are usually narrower 

 at their base than at their summit. They contain a 

 complex capillary plexus (Fig. 248), the terminal loops 

 of which enter the numerous simple papillae that clothe 

 the surface of the fungiform body. Amidst these lie 

 nerve-tubes, which probably terminate in free extremi- 

 ties between the epithelial cells, the epithelium itself 

 being so thin as to allow the red color of the blood to 

 be seen through it. In this manner they are readily 

 distinguished from the filiform papillae, among which 

 they lie. The filiform papillae, like the preceding, con- 

 tain a plexus of capillaries and a bundle of nerve- 

 fibres, both terminating in loops, which enter the sim- 

 ple papillae that clothe the surface of the compound 

 body; but instead of being covered with a thin scaly epithelium, they are 

 furnished with bundles of long pointed processes, some of which approach 

 hairs in their stiffness and structure. These are immersed in the mucus of 

 the mouth, and may be moved in any direction, though they are generally 

 inclined backwards. The simple papillae, which occur in an isolated manner, 

 may not improbably be tactile ; while those which are aggregated in the 

 circumvallate and fungiform bodies, doubtless minister to the sense of Taste, 

 this being most acute in the situations wherein they most abound. With 

 regard, however, to the office of the filiform papillae, there, seems much reason 

 to coincide in the opinion of Messrs. Todd and Bowman : " The compara- 

 tive thickness of their protective covering, the stiffness and brushlike ar- 

 rangement of their filamentary productions, their greater development in 

 that portion of the dorsum of the tongue which is chiefly employed in the 

 movements of mastication, all evince the subservience of these papillie to 

 the latter function, rather than to that of taste ; and it is evident that their 

 isolation and partial mobility on one another, must render the delicate touch 

 with which they are endowed more available in directing the muscular ac- 

 tions of the organ. The almost manual dexterity of the organ, in dealing 

 with minute particles of food, is probably provided for, as far as sensibility 

 conduces to it, in the structure and arrangement of these papillae. It may 

 be added, that the filiform papillae of Man seem to be the rudimentary 

 forms of those horny epithelial processes which acquire so great a develop- 

 ment in the tongues of the Caruivora, and which are of such importance in 

 the abrasion of their food. The mode of termination of the gustatory nerves 

 has been the subject of much recent research. Engelmamr describes the 

 glosso-pharyngeal nerves in Man and Mammals as terminating in peculiar 



1 Szabadfdldy, Virchow's Archiv, xxxviii, p. 177. 



2 Strieker's Manual of Histology, New Sydenhiim Society, 1873, vol. iii, p. 1, 

 where a complete bibliography of the subject is -rivm. The principal English ref- 

 erences are Waller, Philosophical Transact,, 1847; Lionel Beale, idem, 1865, and 

 (Juart. Jonrn. of Microscop. Sci., 18G9 ; and K. L. Maddox, Month. Microscop. 

 Journal, 1869. And since the date of Kngelmann's article, the following papers 

 have appeared: Ajtai, Archiv f. Mic. Anat , Bd. viii, p. 455; Ditlevsen, Underso- 

 gelse, etc., Copenhagen, 1872; Abstract in Schwalbe's Jahresbcricht, 1872; Honig- 

 Bchmeid, /eitsch. fur Wiss. Zool., Bd. xxiii, p. 414; Sertoli, Gaxetta Med.-Vet., 

 Anno iv, Sep. abd. 



