226 ANATOMY FOR NUESES. [Chap. XIX. 



the root, and bearing on their free surface a form of ciliated 

 epithelium. In some animals the hair-like processes on the fili- 

 form papillcB are horny in structure, and their tongues are cor- 

 respondingly roughened, so that they supplement the teeth in 

 the bruising and crushing of food. In man these hair-like pro- 

 cesses are exceedingly delicate, and seem to be specially con- 

 nected with the sense of touch, which on the tip of the tongue 

 is highly developed, and which serves to guide the tongue in its 

 variable and complicated movements. 



In the circumvallate, some of the fungiform papillse, and 

 scattered also over the mucous membrane of the tongue and 

 soft palate, are little clusters of cells lying in cavities of the 

 epithelium, called taste-buds. The bases of these cell-clusters, 

 or taste-buds, are supplied with nerve-fibres. The nerve-fibres 

 are derived from the glosso-pharyngeal and from the lingual or 

 gustatory, a branch of the trigeminal. The former supplies 

 the back of the tongue, and section of it destroys taste in that 

 region ; the latter is distributed to the front of the tongue, and 

 section of it, similarly, deprives the tip of the tongue of taste.^ 



We often confound taste with smell. Substances which have 

 a strong odour, such as onions, are smelled as we hold them in 

 our mouths; and if our sense of smell is temporarily suspended, 

 as it sometimes is by a bad cold in the head, we may eat garlic 

 and onions and not taste them. Hence the philosophy of hold- 

 insf the nose when we wish to swallow a nauseous dose. 



The sense of smell. — The nose is the special organ of the 

 sense of smell. It consists of two parts, — the external fea- 

 ture, the nose, and the internal cavities, the nasal fosste. The 

 external nose is composed of a triangular framework of bone 

 and cartilage, covered by skin and lined by mucous membrane. 

 On its under surface are two oval-shaped openings — the nos- 

 trils — separated by a partition. The margins of the nostrils 

 are provided with a number of stiff hairs which arrest the pas- 

 sage of dust and other foreign substances carried in with the 

 inspired air. 



The nasal fossae are two irregularly wedge-shaped cavities, 

 separated from one another by a partition or septum, and com- 

 municating with the air in front by the anterior nares or nostrils, 



1 The exact location of the cell-bodies, of which these nerve-fibres are the 

 dendrones, is uncertain, as is also the way in which their axones enter the brain. 



