ORGANS OF THE SENSES. 495 



blood-vessels and nerves, arranged in a plexiform manner, 

 from which the papillae are supplied : to its under surface 

 the extremities of the muscular fibres of the muscles of the 

 tongue are firmly attached ; this arrangement imparts to the 

 whole organ a considerable power of movement and of nice 

 adaptation. 



The papillary structure, which is the real seat of the sense 

 of taste, is constituted of an immense number of papillae, 

 which occasion a somewhat flocculent appearance of the whole 

 surface of the tongue. 



The papilla are divisible into simple and compound, and 

 the latter again into filiform, fungiform, and calyciform ; be- 

 sides these several compound forms, however, others exist of 

 no very definite shape, but approaching more or less closely 

 in their characters to either the fungiform or calyciform 

 papilla?. 



The simple papillae exist principally on the sides and under 

 surface of the tongue, but also, though more sparingly, on its 

 upper surface, as between the filiform papilla, in the space 

 around the base of each fungiform papilla, and for a short 

 distance behind the calyciform papillae, and to either side of 

 them. (See Plate LXY. fig. 10.) 



They vary somewhat in size, form, and structure in dif- 

 ferent situations ; in general they are much pointed at their 

 extremities : behind the calyciform papillae they are obtuse 

 and pyriform in shape, (see Plate LXV.jfy. 11.) while on 

 the under surface of the tongue their extremities are very 

 frequently perforated, and they .appear to serve the double 

 purpose of a papilla and mucous follicle. (See Plate LXV. 



fig- 2.) 



They each consist of, in addition to their epithelial invest- 

 ment, a layer of basement membrane, a single looped blood- 

 vessel, filaments of nerves, and granular and nuclear contents. 

 (See Plate LXV. fg. 6. and Plate LXVL fig. 5.) 



The compound papillae are confined to the upper surface 

 and edges of the tongue, and do not extend, except for a 

 short distance at the sides, over the space bounded in front 

 by the calyciform papillae, and behind by the epiglottis. 



K R 3 



