468 



MANUAL OF HISTOLOGY. 



vascular loops are far more numerous than in the first form. The nerves 

 enter the papillae as tolerably strong twigs : the mode of their ultimate 



termination, however, is still undecided. 

 According to Krause, terminal bulbs may 

 be found here ( 184). 



In the third form, finally, the papillce 

 vallatce, s. circumvallatce (fig. 448), we 

 have the largest of all these organs, and 

 probably also the most important, as far 

 as the sense of taste is concerned. In 

 man and the mammalia generally they 

 present many varieties. Their number 

 is small but variable, amounting to from 

 10 to 15. They are arranged at the root 

 of the tongue in a V-shaped figure. Each 

 of the projections (^4) is surrounded by a 

 circular ridge of epithelium (B), into 

 which racemose glands empty themselves 

 (Schwalbe), and supports on its broad 

 surface a multitude of conical accessory 

 papillae (c) overlaid with a smooth stratum 

 of epithelium (a). That eminence which 

 forms the apex of the V-springs fro in the 

 bottom of a deep groove known as the 

 foramen caecum linguis. 



These little organs are abundantly 

 supplied with nerves (b b). The latter 

 form delicate interlacements, from which 

 the primitive tubes are given off whose 

 ultimate distribution will be referred to 

 presently. The annular folds also encir- 

 cling the papillae are likewise richly supplied with nerves (B, b). 



The sources of the nervous supply of these parts are the trigemini and 

 glossopharyngei, the ninth or hypoglossus being simply a motor nerve of 

 the tongue. The anterior part of the dorsum of the organ is innervated 

 by the ramas lingualis from the lower division of the fifth nerve, and by 



the chorda tympani, while 

 the posterior portion is sup- 

 plied by the lingual branch 

 of the glossopharyngeus, 

 which sends its ramifica- 

 tions into the circumval- 

 late papillae. On both of 

 these nerves small ganglia 

 are to be seen. It seems 

 hardly probable that the 

 filiform papillae, clothed as 



they are with a large 



amount of horny epithelium, should be the recipients of the sense of taste 

 (Todd and Bowman). The two other forms seem to preside over the 

 latter as well as the sense of touch. 



The lymphatics of the tongue have been carefully studied by Teicli- 

 mann and Sappey. According to the former, the mucous membrane, and 



Fig. 447. Fimgiform papilla, from tlie 

 human tongue. A, a papilla covered 

 to the left with epithelium, , and 

 over its whole surface with conical 

 smaller papillae, p. B, another, less 

 strongly magnified, with its epi- 

 thelial envelope c, its capillary loops 

 d, artery a, and vein v; e, vascular 

 loops in the adjacent simple papillae 

 of the mucous membrane. Copied 

 from Todd and Bowman. 



Fig. 448. A circumvallate papilla from the human tongue 

 A, with accessory papillae c, its epithelium a, and nervous, 

 twigs 6. B, the ridge running round the papilla, with its 

 nerves b. Copied from Todd and Bowman. 



