THE SENSORIAL FUNCTION. 123 



office is to convey, more perfectly than it could be done through the mere air 

 of the cavity, the vibrations that have reached the membrana tympani. 



These bones are highly elastic ; and covered by a cartilaginous substance, 

 elastic also in the greatest degree, by means of which the force of the vibration 

 is much increased. 



It is conveyed to a strangely irregular cavity, filled with an aqueous fluid, 

 and the substance or pulp of the portio mollis or soft portion of the seventh pair 

 of nerves, the auditory nerve, expands on the membrane that lines the walls of 

 this cavity. 



Sound is propagated far more intensely through water than through air ; and 

 therefore it is that an aqueous fluid occupies those chambers of the ear on the 

 walls of which the auditory nerve is expanded. By this contrivance, and by 

 others, which we have not space now to narrate, the sense of hearing is fully 

 equal to every possible want of the animal. 



The Eye is a most important organ, and comes next under consideration, 

 as inclosed in the bones of the skull. The eye of the horse should be large, 

 somewhat but not too prominent, and the eyelid fine and thin. If the eye is 

 sunk in the head, and apparently little for there is actually a very trifling dif- 

 ference in the size of the eye in animals of the same species and bulk, and that 

 seeming difference arises from the larger or smaller opening between the lids 

 and the lid is thick, and especially if there is any puckering towards the inner 

 corner of the lids, that eye either is diseased, or has lately been subject to 

 inflammation ; and, particularly, if one eye is smaller than the other, it has at no 

 great distance of time, been inflamed. 



The eye of the horse enables us with tolerable accuracy to guess at his temper. 

 If much of the white is seen, the buyer should pause ere he completes his bargain ; 

 because, although it may, yet very rarely, happen that the cornea or transpa- 

 rent part is unnaturally small, and therefore an unusual portion of the white of 

 the eye is seen, experience has shown that this display of white is dangerous. 

 The mischievous horse is slyly on the look out for opportunities to do mischief, 

 and the frequent backward direction of the eye, when the white is most per- 

 ceptible, is only to give surer effect to the blow which he is about to aim. 



A cursory description of the eye, and the uses of its different parts, must be 

 given. 



The eyes are placed at the side of the head, but the direction of the conoid 

 cavity which they occupy, and of the sheath by which they are sur- 

 rounded within the orbit, gives them a prevailing direction forwards, so that the 

 animal has a very extended field of vision. We must not assert that the eye of 

 the horse commands a whole sphere of vision ; but it cannot be denied that 

 his eyes are placed more forward than those of cattle, sheep, or swine. He 

 requires an extensive field of vision to warn him of the approach of his enemies 

 in his wild state, and a direction of the orbits considerably forward, in order to 

 enable him to pursue with safety the headlong course to which we sometimes 

 urge him. 



The eye-ball is placed in the anterior and most capacious part of the orbit, 

 nearer to the frontal than the temporal side, with a degree of prominence vary- 

 ing with different individuals, and the will of the animal. It is protected 

 by a bony socket beneath and on the inside, but is partially exposed on the roof 

 and on the outside. It is, however, covered and secured by thick and powerful 

 muscles by a mass of adipose matter which is distributed to various parts of 

 the orbit, upon which the eye may be readily moved without friction, and 

 by a sheath of considerable density and firmness, and especially where it is most 

 needed, on the external and superior portions. 



The adipose matter exists in a considerable quantity in the orbit of *he eye of 



