‘of the 
oquet® calls this pouch intermaxillary sinus 
or sac. In venomous serpents, the lacrymal 
canal opens, as in the mammifera, in the ex- 
ternal wall of the nasal foss:e. 
_ There is no lacrymal apparatus in fishes. 
In the description of the lacrymal gland in 
man, the intimate structure of it in the lower 
mals has been already alluded to. The re- 
of Miiller may be repeated here, that 
glands have often a perfectly different 
ure in different animals; of which the 
erymal gland examined in the chelonia, birds, 
id mammifera affords an example. 
‘The lacrymal bone contributes to separate the 
tbit from the cavity of the nose. It is wanting 
certain mammifera, as the phoce and most 
facea. It is enormously developed, on the 
y, in certain others, as the giraffe, stag, 
e. It exists also in birds, and forms in them 
fien the greatest part of the inferior margin of 
the orbit. In reptiles, its existence is variable. 
It is found in crocodiles. It is absent in the 
elonia, ophidia, and batrachia. It is also 
nting in fishes, unless the first infra-orbital 
‘assumed as analogous to it. 
ruminating animals, remarkably so in deers 
and antelopes, the infra-orbital fossa of the su- 
perior maxillary bone is very large, and is lined 
y areflection of the skin, more or less in the 
wm of asac. Theskin, which has assumed 
characters of a mucous membrane, contains 
substance numerous follicles,which secrete 
k blackish unctuous humour—a secretion 
h appears to have some relation with the 
function. This matter has been impro- 
called tears, hence the French name 
ers of the infra-orbital glandular sacs of 
minants. In the sheep these organs are re- 
presented by a mere fissure extending on the 
de of the nose from the nasal canthus. 
-Meckel compares to this structure the fovee 
in the face, behind the nostrils, of several poi- 
onous serpents, such as the rattle-snake; but 
Palatine branch of the upper jaw. 
bs 
Ps 
+ 
ars to secrete anything. The temporal gland 
bf the elephant seems to be of the same nature 
s the infra-orbital glandular sacs of rumi- 
nants. 
Development of the accessory parts of the 
eye.+—The accessory parts of the eye appear 
bsequently to the eyeball, and, as is the case 
ith the accessory parts of the organ of hearing 
n reference to the labyrinth or ear-bulb, have 
“quite a separate and distinct origin from it. 
That the development of the accessory parts of 
he eye is independent of that of the eyeball is 
_ confirmed by the anomalous conformation which 
| the organ has been sometimes found to present; 
' thus Malacarne relates a case in which the eye- 
_ balls, their nerves and muscles were wanting, 
f whilst the lacrymal apparatus and eyelids were 
regularly developed. 
_ Up to the eighth week the external integu- 
. 
ca 
| * Op. cit. 
_ + Burdach, Die Physiologie, als Erfahrungs- 
) wissenschaft, &c. and Valentin, Entwickelungs- 
-geschichte. 
LACRYMAL ORGANS. 
¢ membrane lining these parts scarcely ap- 
99 
ment passes quite smoothly over the eyeball. 
The conjunctiva is then partitioned off by the 
formation of a linear fold, which, in the ninth 
week, surrounds the anterior surface of the 
eyeball like a small ring. The upper and lower 
parts of the fold progressively enlarge until 
they meet each other over the eyeball, which 
takes place about the twelfth week. 
The progress of the development of the eye- 
lids is sometimes arrested, so that mere folds of 
skin have been found occupying their places, or, 
development having proceeded a little further, 
the eyelids have been found presenting their 
regular conformation indeed, but too short to 
cover the eyeball and incapable of motion. 
Having met, the edges of the eyelids ad- 
here by the extension of the epidermis from 
the one to the eter. In the human embryo 
the adhesion between the eyelids by the exten- 
sion of the skin ceases towards the latter 
months, but the edges continue sticking together 
by the Meibomian secretion until the period of 
birth. In the young of several of the mammi- 
fera, as the carnivora and rodents, the eyelids 
continue closed for some time after, birth— 
from one to two weeks. In birds, even in the 
embryo state, the eyelids never unite. 
Sometimes adhesion between the eyelids in 
the human subject is found at birth, constitut- 
ing what is called congenital anchyloblepharon ; 
and this may be either immediate or by the 
intervention of a membranous structure. 
The closure of the pupil by the pupillary 
membrane in the fcetus corresponds to the ad- 
hesion of the eyelids to each other at that period. 
According to Meckel the pupillary membrane 
continues entire in animals born blind, as it is 
expressed, as long as the eyelids remain closed. 
The tarsal cartilages first appear distinctly in 
the fifth month; and at birth, that of the up- 
per is perfectly developed. The eyelashes first 
appear free about the sixth month. 
The lacrymal gland is already evident in the 
last half of the fourth month. 
The inner canthus of the eye is at first more 
elongated than it is afterwards. 
On the ‘first appearance of the eyelids, 
Burdach tells us, the lacrymal caruncle presents 
itself; and at the inner angle a diverticulum of 
the conjunctiva sinks down to the oro-nasal 
cavity as the commencement of. the lacrymal 
sac and nasal duct. The lacrymal points 
project very much in the fifth month, and in 
the seventh are somewhat more retracted. The 
lacrymal apparatus in general, as also the 
Meibomian follicles, are proportionably much 
developed at an early period. 
BIBLIOGRAPHY.—See that of article Eye and 
the several works referred to in the course of 
this. The most complete, indeed, so far as 1 
know, the ony monography, is that of John Chris- 
tian Rosenmiiller, ** Partium externarum oculi ha- 
mani imprimis organorum lacrymalium descriptio 
anatomica, iconibus illustrata.” Lipsie, 1810. In 
this will be found a catalogue raisonné of all pre- 
ceding works bearing on the subject. 
(T. Wharton Jones.) 
H 2 
