THE SENSORIAL FUNCTION. 155 



of the cartilage are numerous glands that secrete or throw out a scaly 

 white greasy matter, which may be rubbed off by the finger, and is 

 destined to supple this part of the ear, and to keep it soft and smooth. 

 Below this are other glands, which pour out a peculiar, sticky, bitter fluid 

 — the wax — probably displeasing to insects, and therefore deterring them 

 from crawling down the ear and annoying the animal, or by its stickiness 

 arresting their progress. 



The internal part of the couch is covered with long hair, which stands 

 across the jiassage in every direction. This hkewise is to protect the ear 

 from insects, that can with difficulty penetrate through this thick defence. 

 The cold air is likcAvise prevented from reaching the interior of the ear, 

 and the sound is moderated, not arrested — penetrating readily but not 

 violently — and not striking injuriously on the membrane covering the 

 drum of the ear. Can these purposes be accomplished when it is the 

 custom of so many cartel's and grooms to ctit out the hair of the ear so 

 closely and industriously as they do ? The groom who singes it to the 

 root with a candle must either be very ignorant or very brutal. It can 

 scarcely be accomplished without singeing the ear as well as the hair. 

 Many a troublesome sore is occasioned by this ; and many a horse that 

 was perfectly quiet before rendered difficult to handle or to halter, and 

 even disposed to be otherwise vicious, from a recollection of the paiji 

 which he suffered during the absui'd and barbarous operation. 



The sound collected by the outer ear passes through the lower or 

 annular, ring-shaped cariilacje, and through irregularities which, while 

 they break and modify it, convey it on to another canal, partly cartilagi- 

 nous and partly bony, conducting immediately to the internal mechanism 

 of the ear. This canal or passage is called the external auditory passage, 

 and at the base of it is placed, stretching across it, and closing it, a thick 

 and elastic membrane, membrana tympani, called the membrane of the 

 drum. This membrane is suppHed with numerous fibres, from the fifth 

 pair, or sensitive nerve of the head, for it is necessary that it should pos- 

 sess extreme sensibility. 



Between this membrane and a smaller one almost opposite, leading to 

 the still interior part of the ear, and on which the nerve of hearing is ex- 

 panded, are four little bones, united to these membranes and to each other. 

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

 mere air of the ca\aty, the vibrations that have reached the membrana 

 tympani. 



These bones are connected together, and are covered by a cartilaginous 

 substance, elastic in the greatest degree, by means of which the force 

 of the vibration is much increased. 



It is conveyed to a strangely iri'egular ca\'ity, filled with an aqueous 

 fluid, and the substance or pulp of the portio mollis or soft portion of the 

 seventh paii- 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 on which the auditory nerve is expanded. By 

 this contrivance, and by others, which we have not space now to nar- 

 rate, the sense of hearing is fully equal to every possible want of the 

 animal. 



The JiJye is a most important organ, and comes next under considera- 

 tion, as enclosed 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 upparently little — for there is actually a 

 very trifling difiercnce in the size of the eye in animals of the same species 



