284 GENERAL ORNITHOLOGY part ii 



branches of the glossopharyngeal nerve which go to the l^ack part of 

 the tongue and mouth. Though the chorda tympani nerve exists, 

 there is no lingual (gustatory) branch of the third division of the 

 fifth cranial nerve. Yet the latter, which goes in mammals to the 

 anterior part of tlie tongue, is less effectually gustatory than the 

 glossopharyngeal ; as we know by the fact that the sensation of 

 taste is not completely experienced until the sapid substance passes 

 to the back of the mouth. Gustation is likewise connected with 

 olfaction ; the full effect of nauseous substances, for example, being 

 not realised if the nose is held. From these alternative considera- 

 tions, each one may estimate for himself how much birds know of 

 sapidity ; remembering also, how soft, thick, and fleshy are the 

 tongue and associate parts in some birds, as parrots and ducks, in 

 comparison with birds whose mouths are quite horny. 



The beak is doubtless the principal tactile instrument ; nor does 

 its hardness in most birds preclude great sensitiveness ; as witness 

 the case of the teeth, above instanced. Sensation is here governed 

 by the branches of the fifth nerve. In some birds, in which also 

 the terminal filaments of this nerve are largest and most numerous, 

 the bill acquires exquisite sensibility. Such is its state in the snipe 

 family, in most members of which, as the woodcock, true snipe, and 

 sandpipers, the bill is a very delicate nervous probe. The Ajyteryx 

 also feels in the mud for its food, enjoying moreover the unusual 

 privilege of having its nose at the end of its long exploration. 

 Ducks dabble in the water to sift out proper food between the 

 " strainers " with which the sides of their beaks are provided ; and 

 the ends of the maxillary and mandibular bones ^themselves are full 

 of holes, indicating the abundance of the nervous supply (Fig. 63). 



The senses of birds and other animals are commonly reckoned 

 as five — a number w^hich may be defensively increased — as by a 

 sixth, the muscular sense, which gives consciousness of strain or 

 resistance, apart from purely tactile impressions ; and perhaps a 

 seventh, the faculty of equilibration, which has a physical mechan- 

 ism of its own, at least as distinct and complete as that of hearing. 

 The ordinary " five senses " are curiously graded. Taction connotes 

 qualities of matter in bulk, as density, roughness, temperature, etc. 

 Gustation, matter dissolved in water — fluidic. Olfaction, matter 

 diffused in air — aeriformed. Audition, atmospheric air in undula- 

 tion. Vision, an ethereal substance in undulation. All animals 

 are probably also susceptible of hiogenation, which is the affection 

 resulting from the influence of biogen ; a substance consisting of 

 self-conscious force in combination with the minimum of matter 

 required for its manifestation.^ 



^ Tlie reader who may be interested to inquire further in this direction is referred 

 to a publication entitled: — Jiiogeii : A Speculation on the. Origin and Nature of Life. 



