78 THE EiORSE. 



likMM'se supported and moved by a third small cartilage, placed at the 

 fore part ot" tlie base of the conch, and into which several muscles are 

 inserted. 



The car is covered by a skin thinner than in most other parts of the body, 

 and altogetiier destitute of fat, that it may not be too bulky and heavy, and 

 n-.av be more easily moved. Under the skin lining the inside of the car- 

 tilage are more numerous glands, that secrete or throw out a scaly, white, 

 greasy matter, which may be rubbed off with the finger, and which is des- 

 tined 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 conch is covered with long hair, which stands 

 across the passage in every direction. This likewise is to protect the ear 

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

 The cold air is likewise 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 carters and grooms to cut the hair out of the ear so closely and indus- 

 triously as they do ? The groom who singes it to the roots with a candle 

 must either be very ignorant or very brutal. It can scarcely be accom- 

 plished without singeing the ear as well as the hair. Many a troublesome 

 sore is occasioned by it ; and many a horse that was perfectly quiet before, 

 rendered difficult to handle or halter ; and even disposed to be otherwise 

 vicious from a recollection of the pain which he suffered during the absurd 

 and barbarous operation. 



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

 ring-shaped cartilage, and through irregularities which, while they break 

 and modify it, carry it on to another canal, partly cartilaginous and partly 

 bony, conducting immediately to the internal mechanism of the ear. This 

 canal or passage is called the external auditory passage, a ; and at the base 

 of it is placed, stretching across it, and closing it, a thick and elastic mem- 

 brane, called the membrane of the drum, h. This membrane is supplied 

 with numerous fibres, from the fifth pair, or sensitive nerve of the head, for 

 it is necessary that it should possess extreme sensibility. 



The mechanism of the ear is so exquisite that we cannot refrain from 

 entering into a minute description of it, although we feel that we are some- 

 wiiat trenching on the comprehensive subject of animal physiology. 



Sound is produced by certain vibrations or undulations communicated to 

 the air, by the concussions or tremblings of things around, and which 

 vibrations spread through the air, and fall upon the ear. The striking of 

 a glass, and the souiW of a large bell, are sufficient illustrations of the 

 manner in which sound is propagated by distinct vibrations or waves of the 

 air. These vibrations reach the conch of the ear. From its hollow form 

 and peculiar shape, and the faculty of being directed to every quarter 

 whence the vibrations proceed, they are collected, and condensed, and con- 

 veyed down the outer passage, and fall upon the membrane, b. That 

 membrane, tightly stretched, and elastic, receives the impression made 

 upon it, and vibrates in perfect unison. 



This membrane covers the entrance into a cavity, called the tympanum 

 or drum of the ear, I, from its supposed resemblance to a drum. It is of 

 an irregular shape. The walls or sides are composed of bone, lined with a 



