262 
OBSERVATIONS ON SOUNDNESS. 
liquor Morgagni, and is retained in its place by the attachment 
ot the zonula ciliaris. The lens consists of concentric layers, 
of which the outer are soft, the next firmer, and the central 
form a hardened nucleus. These layers are best demonstrated 
by boiling. 
The appendages of the eye are placed in close approximation 
to the globe ; they are divided into external and internal. The 
upper and lower lids unite and form the canthi; the lids 
possess a muscular power of closing and opening; they can 
shut out all offending agents; they are the regulators of the 
rays of light. The muscles of the lid are not voluntary ; the 
superior lid is more strongly developed than the inferior, it 
has more motion also. From the outer surface of the lid are 
growing long hairs ; they must be intended for some specific 
purpose, and they doubtless are for the purpose of protecting 
the organ from insects, hay-seeds, &c.; each one conveys sen¬ 
sation ; they were by the late Professor Coleman called 
watch-dogs of the eye; they ought never to be cut away. These 
hairs are also found on the under lid, but not so numerous. 
The range of hairs upon the upper lid are performing the 
office of shrouding the eye from the rays of light coming from 
above, which are more powerful than those coming from 
below ; the other appendages are the eyelashes, the caruncula 
lachrymalis, and the lachrymal apparatus, together with the 
conjunctiva. Meibomian glands, cartilages (the horse has no 
tarsal cartilages), cellular membrane, arteries, veins, nerves, 
absorbents. The tegumentary cellular tissue of the lids is very 
loose, and is remarkable for the absence of fatty matter; it 
is very liable to serous infiltration. The Meibomian glands 
secrete a mucus to prevent impediment in opening the lids. 
The conjunctiva is the mucous membrane of the e 3 ’e, it is 
found to cover the whole of the anterior surface, and is then 
reflected upon the lids, so as to form their internal layer to the 
cartilago-nictitans, and passes down to give a lining to the 
ductus ad nasum. It is most vascular where it lines the lids; 
where it covers the cornea it is very thin and closely adherent, 
and no vessels are seen there in the absence of inflammation; 
it differs from mucous membranes in being transparent. 
The caruncula lachrymalis is a little tubercle situated on the 
inner canthus; it is principally covered by common integu¬ 
ment, a very small portion only being covered by the con¬ 
junctiva. It is intended for the purpose of directing the 
tears into the puncta lachry^malia. In man it is said to be 
glandular. 
The lachrymal gland Is situated underneath the orbital arch ; 
to gain a view of it the removal of the bone is necessary; 
