94 
ment, uced partly by the vessels crossi 
over RL ereirec sept, and partly by thoweis: 
lations. The latter is particularly the case 
around the cornea. It is only in the inflamed 
state—in catarrhal ophthalmia—that the vessels 
of the ocular conjunctiva can be well seen. 
In catarrhal opbthalmia, large superficial tor- 
tuous vessels are observed proceeding in a di- 
rection towards the cornea; a few of the same 
Size are seen crossing these, especially at a dis- 
tance from the cornea. Underneath the large 
vessels is a network of smaller ones, the 
branches of the larger. The arrangement of 
the vessels around the margin of the cornea 
has been already noticed. It can scarcely be 
doubted that the large dark-coloured varicose 
vessels, derived from the muscular, seen in the 
conjunctiva in the so-called arthritic states of 
the eye, are veins, as also the largest and most 
tortuous of those seen in catarrhal ophthalmia. 
Of the two sets of vessels distributed to the 
conjunctiva, one set supplies the conjunctiva 
ager the palpebral sinuses, the other that 
part of the conjunctiva which corresponds to 
the tarsal cartilages. Both sets give off nu- 
merous branches, which subdivide very mi- 
nutely in the papillary body. The second set, 
having given off their ramifications to the 
papillz, proceed towards the margins of the 
eyelids ; following, in the upper, a straighter 
and more parallel direction than in the lower. 
2. Veins.—The veins from the eyelids dis- 
charge their blood into the anterior and pos- 
terior facial veins. 
The blood from the other accessory parts of 
the eye is returned to the cavernous sinus by 
the ophthalmic veins, of which there are two 
to each eye:—one called the cerebral oph- 
thalmic, and the other the facial ophthalmic 
vein. 
Cerebral ophthalmic vein.—Larger than the 
facial ophthalmic vein, this begins at the inner 
angle of the eye, from the upper end of the an- 
terior facial vein. From this it passes back- 
wards through the orbit to the inner part of the 
superior orbital fissure, by which it enters the 
cranium, where it empties itself into the caver- 
nous sinus—seldom into the circular sinus. 
In this course it has several communications 
with the facial ophthalmic. The cerebral oph- 
thalmic vein receives directly or indirectly, 
besides the veins from the different parts of the 
eyeball and its muscles, a vein from the lacry- 
mal sac, and from the parts lying at the inner 
canthus ; the anterior nasal vein, the lacrymal 
yein, and the posterior nasal vein. 
Facial ophthalmic vein.—This receives the 
infra-orbital and some other deep veins of 
the face, besides some veins from the eyeball. 
The deep branch of the anterior facial vein 
takes one of its origins from it. The facial 
ophthalmic vein leaves the orbit by the supe- 
rior orbital fissure, and opens into the cavernous 
sinus below the cerebral ophthalmic. 
Comparative anatomy and development.— 
In ‘the description just given of the accessory 
parts of the human eye, allusion has been occa- 
sionally made to their structure in the lower 
animals; here such further observatjens will be 
LACRYMAL ORGANS. 
offered as may tend to illustrate_their physic 
gical importance in the animal series, 
And first, it may perhaps be well to’ ee] 
mind that, although generally speaking, or 
traced from the higher to the lower animals 
observed to become depreciated in dey 
ment; still that this is by no means ali 
the case in a ratio corresponding to 
tion of the animal in our classifications. 
the circumstances connected with the me 
life of an animal, be it mammal, bird, rep 
or fish, may be such as to call for a great 
less development of some pear 0 
Thus, though in the mammifera we find 
eyelids very perfectly developed, and in 1 
in an extremely imperfect state, or ent 
wanting, and though we find gradatior 
tween these two extremes in the 
ing an intermediate place, still there ¢ 
mammiferous animals in which the in gull 
passes right over the eyeball without form 
any palpebral fold; and there are fishes 
which there are not only palpebral folds, 
also an orbicular muscle, Again, the s 
lunar fold of man and the higher quad: 
is enlarged in quadrupeds into the membr 
nictitans, and in birds forms the very artifict 
constructed third eyelid, which subsists, th 
in a less perfect state, in reptiles, but in fis 
where the structure does exist, it is found a 
reduced toasemilunar fold. In man thela 
mal gland is large. In the lower mammi 
generally, in birds, and in the higher 
lacrymal gland is also found, But it is si 
in proportion to another gland situated at 
nasal canthus of the eye, the glandule 
Harder, which is developed in a direct pro 
tion with the membrana nictitans, or third ¢ 
lid, and to which it therefore belongs. I 
and the quadrumana there is no trace of 
glandule of Harder. It is incorrect to view" 
lacrymal caruncle in that light, for both 4 
exist together. 
Besides these differences in the developmi 
of the accessory parts of the organ of vis 
observed in the animal series and capabl 
being generalised, there exist specific ar 
vidual differences which can only be notice: 
detail. 4 
1. Eyelids. 
In subterranean mammifera, as the blind 
the chrysochloris of the Cape, the comm 
mole ; among reptiles, in the pipa, which I 
in obscure places; and in perennibranehi 
batrachia, which inhabit subterranean I 
or marshes, as the proteus and syren; an 
fishes which burrow in the mud or sand. 
the anguilliform and certain cyclostoma 
fishes, the eyes are very small, and the comt 
integument passes right over them w. 
forming any palpebral fold. In the Ophi 
reptiles as first pointed out by Jules Cloc 
in Geckoes among the Saurian les, 
shewn by J. Miiller ; and even in the blind1 
according to the latter author, there is a €ol 
pounding of the simple continuation of thei 
teguments over the eyeball, as described ab 
with the existence of a conjunctiva undernea 
enclosing an oculo-palpebral space. Thiss 
“1... 
—3bi8 
Ppt 
