STRUCTURE OF THE HUMAN BODY 



55 



Fig. 30. — Section of Papillse of the Tongue— highly magnified 



I A, Section of the central papilla; b b, section of the surround- 

 ing elevation; Pa, papilla of the dermis; Ep, layer of epithelium; 

 T, taste buds; II and ill represent very highly magnified views of 

 cells of the taste buds. Note their oval nuclei. 



which are imbedded minute ovoid taste-buds containing slender 

 taste-cells. These cells are connected with nerve -fibres which 

 have been usually regarded as coming from the ninth cranial 

 nerve, though there is reason 

 to believe that they really 

 belong to the fifth. How- 

 ever that may be, there are 

 only two sensations of taste 

 proper, i.e. sweetness and 

 bitterness, and the stimulus 

 which initiates either of 

 these must be something in 

 a dissolved condition. Many 

 so-called tastes are partly 

 smells, and that such "fla- 

 vours " are of this mixed nature is practically demonstrated by 

 a cold in the head, which largely destroys what we popularly call 

 taste, although only the nose is affected. We are able to smell 

 the food in the mouth by reason of the fact that mouth-cavity and 

 nasal cavities alike communicate with 

 the pharynx (see p. 34). It must also 

 be borne in mind that the lining of 

 the mouth, especially that part of it 

 covering the tongue, also ministers 

 to the sense of touch. The tip of 

 the tongue is even more sensitive in 

 this respect than a finger-tip, and 

 there is also good reason for thinking 

 that what we call "acid tastes " are 

 more properly to be regarded as 

 varieties of touch. 



o-*/ r* y*o 77/11— -,\ Fig. 31. — Distribution of Nerves over interior of 



I he benSe OJ ^UneLL (rig. 31;. * Nasal cavity, outer wall 



The OrgranS of smell have to do i, Branches of nerves of smell-olfactory nerve; 



o 2, nerves of touch to the nostril; 4, s, 6, nerves to 



with teStinSf the quality of the air the palate springing from a ganglion at S; 3, 7, 9, 

 o ^ J ^ ^ branches from one of the palate nerves to nostrils. 



taken into the lungs, and it is there- 

 fore natural that they should be situated at the beginning of 

 the breathing passages. They consist of the two cavities of 

 the nose, opening behind into the pharynx. The mucous mem- 

 brane which lines the upper part of these cavities contains 

 numerous slender olfactory cells, which are the end-organs of 



