REMARKS AND EXAMINATIONS ON THE EYE. 



The parts which compose the eye are 

 divided into external and internal. The 

 external parts are : First, the eyelashes, or 

 cilia, which, in the horse, can scarcely be 

 reckoned more than one, there being very 

 few hairs in the under eyelid. Secondly, 

 the eyelids, or palpebrse, upper and under : 

 where they join outwardly, it is termed the 

 external canthus, and inwardly toward the 

 nose, the internal canthus : they cover and 

 defend the eyes. The cartilaginous margin 

 or rim of the eyelid, from which the eye- 

 lashes proceed, is named tarsus. In the 

 tarsus and internal sm-face of the eyelid 

 there are small glands, which secrete a fluid, 

 to prevent friction of the eye and its lids, 

 and facilitate motion. Thirdly, the lachry- 

 mal gland, which is placed on the upper part 

 of the eyelid toward the external canthus ; 

 from this gland the tears are secreted, and 

 conveyed to the inner surface of the upper 

 eyelid by several minute ducts, or canals, 

 named lachrymal ducts. There is another 

 small body, having a glandular appearance, 

 in the inner corner of the eye ; on each side 

 of which there are smaU orifices which are 

 called puncta lachrymalia: these are the 

 mouths or openings of two small canals, 

 which, joining together, form a membranous 

 tube ; and this, passing through a small open- 

 ing in the bone, extends to the lower part 

 of the nostril, where its termination may be 

 distinctly seen in the horse. As the lachry- 

 mal gland is constantly forming tears, it 

 must be obvious that some contrivance is 

 necessary to convey them off, and prevent 

 them flowing over the cheek : this purpose 

 is answered by the canal just described. 



When any irritating matter is applied to 

 the eye, the tears are formed too abundantly 

 to be carried off in this way; they then 

 flow over the cheek. In the human eye, 



the puncta lachrymalia terminate in a small 

 sac, from which the lachrymal duct proceeds : 

 this is not the case in the horse. In the 

 inner corner of the horse's eye is placed a 

 body commonly termed the haw, no resem- 

 blance to which is to be found in the hu- 

 man eye. The horse has the power, by 

 means of the muscles of the eye, to bring 

 the haw completely over its surface ; it 

 serves, therefore, as a second eyelid, and 

 effectually wipes off any dust, hay, or seeds, 

 or other matter which may have fallen upon 

 the eye. The conjunctive membrane, or 

 tunica conjunctiva, lines the inner surface 

 of the eyelids, and covers the white part of 

 the globe of the eye. This membrane has 

 numerous blood-vessels, which are conspicu- 

 ous when it is inflamed. The bulb or globe 

 of the eye is composed of several coats and 

 humors. The transparent cornea, which, 

 in the horse, forms the front part of the eye, 

 comprehends a larger part of the globe 

 than in the human subject ; on removing 

 this cornea, a fluid, which is named the 

 aqueous humor, escapes, and the iris ap- 

 pears. The iris is a muscular curtain, 

 having a hole in the centre, which is termed 

 the pupil. This divides the fore part of the 

 eye into two parts, named chambers, which 

 are occupied by the aqueous humor. The 

 pupU is of a dark bluish cast ; is of an oval, 

 or rather of an oblong, form. The iris regu- 

 lates the quantity of light that is required 

 to pass through the pupil. For this purpose, 

 it is composed of two sets of muscular 

 fibres : by means of one the pupil is en- 

 larged, and by the other it is diminished. 

 Thus, if the pupil is first examined in the 

 stable, where there is a moderate light, and 

 immediately after in the sunshine, it will be 

 found quite altered; being so small, in a 

 strong light, as to be nearly closed. On re- 



