358 ELEMENTARY PHYSIOLOGY 



that the muscles themselves possess nerve fibres which 

 are certainly afferent, i.e. sensory ; and similarly afferent 

 fibres, connected with extremely minute end-bulbs, are 

 distributed to the tendons. And there is but little doubt 

 that we must look to the impulses generated in these 

 nerves, more especially the nerves of the tendons, as 

 providing the sensations which form the basis of the 

 muscular sense. 



7. The Sense of Taste.— The organ of the sense of 

 taste is the mucous membrane which covers the tongue, 

 especially its back part, and the hinder part of the 

 palate. Like that of the skin, the deep, or vascular, 

 layer of the mucous membrane of the tongue is raised up 

 into papillae ; but these are large, separate, and have 

 separate coats of epithelium. Towards the tip of the 

 tongue they are for the most part elongated and pointed, 

 and are called filiform ; over the rest of the surface of 

 the tongue these are mixed with other large papilL-e, with 

 broad ends and narrow bases, called fungiform ; but 

 towards its root there are a number of larger papillae, 

 arranged in the figure of a V with its point backwards, 

 each of which is like a fungiform papilla surrounded by a 

 wall. These are the circumvallate papilhe (Fig. 113, 

 G.p.). The larger of these papilhe have subordinate small 

 ones upon their surfaces. 



In both the fungiform and circumvallate papillae, the 

 cells which are specially concerned in giving rise to sensa- 

 tions of taste are arranged in bulbous groups, somewhat 

 like the leaves in a bud, and hence these groups are known 

 as taste-buds. In the circumvallate papillae these 

 taste-buds lie imbedded in the layers of epithelium 

 which cover the sides of each papilla. 



Each "bud" is flask-shaped and consists of an outer 

 wall, made up of elongated cells placed side by side like the 

 staves of a barrel, and leaving an opening at the end of 

 the bud where it comes to the surface of the papilla. The 

 inside of the bud is filled with the true gustatory cells, 



