252 THE HUMAN SPECIES 



bees and wasps. As to the gustatory organs in Vertebrates, 

 including man, their histological structure is well enough known, 

 but we are quite in the dark as to the real nature of the sense 

 of taste ; so far we do not even know whether different taste- 

 cells correspond to various tastes or whether a single taste-bud 

 can discriminate more than one sort of flavour. 



Taste-papillae are found in man on the posterior part of the 

 tongue, on the soft palate (but not on the fauces), on the pharyn- 

 geal wall, and the hinder aspect of the epiglottis. In the 

 larynx sweet and bitter can be distinguished, and in children 

 the sense of taste extends to the middle of the tongue and the 

 muceous membrane of the cheeks. The tonsils, palato-glossal 

 fold and hard palate are debatable regions. 



Man's sense of taste is limited to distinguishing salt, acid, 

 sweet and bitter, but as in animals only when the substances 

 in question are dissolved. It is not known whether animals 

 have any other taste-perceptions. At any rate they are like 

 human beings in that smell assists taste in the choice and selec- 

 tion of food. 



If the number of taste-buds bears any direct relation to the 

 taste capacity, man enjoys no supremacy, for the circumvallate- 

 papillae of the ox contain 1760 more taste-buds than those of 

 man. 



In judging of the gustatory powers of certain races great 

 caution is necessary, for although some primitive savages have 

 no names for this or that taste (e.g., the Papuans have no word 

 for bitter), still this does not prove that the perception is lacking. 



The chief nerve of taste is the glossopharyngeal (ninth) ; 

 the accessory nerves are the lingual branch of the fifth and the 

 superior laryngeal branch of the vagus (tenth). 



(e) Tactile and Temperature Sense. 



The tactile sense is common to the whole animal kingdom ; 

 in fact, there are many reasons for thinking that the other 

 senses have been developed from this one. In man}- of the 

 lower species (Invertebrates) the whole body-surface is covered 

 with fine bristles and is exceedingly sensitive ; in insects and 

 crustaceans the chitinous coat is pierced by bristles (hairs) 

 which are connected with nerves. We have learnt to recognise 



