Taste. 485 



auditory, and olfactory organs are supplied with heavy nerve trunks, 

 proceeding from the brain, which are devoted exclusively to the work of 

 their respective senses. The optic nerve has no branches till it reaches 

 the retina. The olf actor} r divides into three branches, all of which enter 

 the nose and are distributed on the pituitary membrane, the septum, 

 and the outer walls of the nasal openings, respectively. Only the first 

 of these divisions ministers to the actual function of smell, but in all 

 probability they all did in the ancient history of the race, or its ances- 

 tors, and now represent a function, altered or decayed, through the 



M 



FIG. 229. Showing Current of Electricity generated by placing 

 ^ ie ton s ue between two plates, one of Copper and the other of Zinc. 

 Current passes from the zinc to the copper. 



FIG. 229. 



changed habit of the race. The auditory nerve beginning in the medulla 

 oblongate, has no branches till it reaches the ear, where it divides into 

 two, one going into the cochlea and the other to the vestibule of the 

 ear. But the nervous functions of the sense of taste appear to be di- 

 vided between two nerves, neither of which constitute an independent 

 and exclusive trunk. One of these is one of man}" sub-divisions of the 

 glosso-pharyngeal ( or 9th pair ). This pair, besides sending some fibres 

 to the papillae on the posterior part of the tongue, also supplies the mus- 

 cles of the pharynx and tongue, the mucous glands of the mouth, and 

 sends numerous connections to other parts. The second taste nerve is 

 one of fourteen branches of the trifacial, or 5th pair. Other branches of 

 this nerve go to the eyelids, forehead, nose muscles, eye muscles, upper 

 and lower teeth, upper lip and cheek, four muscles of the lower jaw, 

 and to the shell of the ear. These comparatively uninfluential taste 

 nerve connections, and the heterogeneous compan}' in which they are 

 found, lead to the suspicion that their adoption of their present func- 

 tions, has been a comparativel}' recent event, most likely not dating back 

 of the mammal tribes. In short, these are old afferent nerves of touch, 

 the functions of which have become changed to afferents of taste with- 

 out alternation of their anatomical position. In the mammal embryo, 

 the nerves of taste do not correspond to an isolated part of the brain, 

 as do the olfactory nerves ( Agassiz ). If, as before suggested, the 

 lislu's do their t<mt lay chiefly through the nasal grooves and the olfactory 

 lubes, it would follow that in the mammal families the fish organ of 

 taste has been modified from a taste organ in the water to a smell organ 

 in the uir, and such modification, so necessary, obvious, and easy, has 

 loft its tracks in the remains of taste functions that still appertain to 

 the sense of smell, as we have it. The tongue of fishes, in such case, 

 might be anticipated to be destitute of a taste sense, and so, for the most 

 part, it is. In general, their tongues arc cartilaginous and often covered 



