86 THE ANATOMY OF VEETEBEATED ANIMALS. 



cation extends into the sides and floor of the tympanum 

 and external meatus ; and a process of integument, chiefly 

 dei'ived from the second visceral arch, is conyerted into a 

 concha, or external ear. 



The Organ of Taste is the mucous membrane which covers 

 the tongue, especially its posterior region, and probably also 

 a part of that lining the fauces. When the sense is well 

 developed, the mucous membrane is raised into numerous 

 papiUse of various forms, and is well supplied with filaments 

 from the glossopharyngeal nerve. 



The sense of Touch is diffused over the integument and 

 over the mucous membrane of the buccal cavity, which is, 

 strictly speaking, a part of the integument. 



As special organs of toiich in the higher Vertehrata, the 

 nei^vous papillBe, containing " tactile cwpuscles,'' and the 

 long facial hairs, the papillae of which are well supplied with 

 nerves, termed vibrissce, may be mentioned. 



In most, if not all Fishes, the integument of the body 

 and of the head contains a series of sacs, or canals, usually 

 disposed symmetrically on each side of the middle line, and 

 filled with a clear gelatinous substance. The walls of the 

 sacs, or canals, are abundantly supplied with nei-ves, and 

 the terminations of the latter enter rounded papillae, which 

 project into the gelatinous contents. These sensory organs 

 are known as the " organs of the lateral line," or " mucous 

 canals ;" and they were formerly supposed to be the secre- 

 tory glands of the sKmy matter which coats the bodies of 

 fishes, and which is really modified epidermis. 



The Alimentary Canal. — This part of vertebrate organi- 

 zation always exhibits a differentiation into mouth, pharynx, 

 oesophagus, stomach, and intestine ; and the last has always 

 a median, or nearly median, aperture on the ventral surface 

 of the body. It may open by itself; or into a cloaca, or 

 chamber common to it, the urinary, and the genital organs. 



The intestine is generally distinguishable into small and 

 large ; and, at the jimction of the two, one or two cceca are 

 frequently developed from the former. 



