98 
as several scinci, which may be drawn over the 
eye without interrupting vision, the cornea cor- 
responding to it.” This is the structure in the 
frog ; for what Cuvier admitted as a third eye- 
lid is horizontal instead of vertical, and, as 
Carus has shown, nothing more than the lower 
eyelid. In the frog the upper eyelid follows 
the motions of the eyeball. e lower eyelid 
has independent motion; admitting of being 
drawn over the eye and falling into a fold when 
this is open. 
The anterior and posterior semilunar folds in 
certain fishes have been already alluded to. 
The glandule of Harder—The glandule of 
Harder belongs peculiarly to the membrana 
nictitans or third eyelid ; it therefore does not 
exist in man and the quadrumana. The lacry- 
mal caruncle is not the representative of it, as is 
asserted in Dr. Grant’s Treatise on Compara- 
tive Anatomy, for both may exist together. I do 
not even know if it is correct to say that the 
two structures are developed in an inverse 
ratio, for in the sheep, in which the glandule of 
Harder is of considerable size, the caruncula is 
absolutely as great, if not greater, than that of 
man. Even among the hare kind, which have 
the membrana nictitans and glandule of 
Harder much developed, 1 find, particularly 
in the rabbit, a trace of lacrymal caruncle as 
scattered follicular grains along with small 
hairs at the inner canthus. It is only in birds 
that we lose all trace of the lacrymal caruncle. 
The glandule of Harder is situated in the 
orbit between its inner wall and the globe of 
the eye. Inthe sheep, for instance, the glan- 
dular substance is collected around the cartila- 
ginous pedicle of the membrana nictitans, 
on the inner surface of which it opens by two 
or three small ducts. In the elephant, in which 
the lacrymal gland is said to be wanting, or 
very small, the glandule of Harder is said to 
be very large. It opens between the membrana 
nictitans and the eyeball by an opening the 
size of a quill. Inthe hare kind, as has been 
said, the glandule of Harder is immense. It 
presents two lobes, and its duct opens in a 
wide lacuna within the membrana nictitans. 
According to Miiller,* the elementary particles 
or ends of the ducts are minute vesicles every- 
where equal and joining in the manner of 
branches into irregular oblong lobes. The 
excretory duct at the external surface of the 
gland opposite the eye is divided in the bi- 
lobated glandular mass into a great number of 
smaller ducts, which divaricating are joined 
each to a branch of the lobules. 
In birds the glandule of Harder is commonly 
much more considerable than the lacrymal 
gland. It lies as usual at the nasal canthus 
and opens within the third eyelid towards the 
eyeball. There is never any caruncle. Miiller 
tells us the glandule of Harder in birds is 
easily injected with mercury after its secretion 
has been all pressed out. The surface of the 
organ is divided into many smaller lobes. The 
internal ramification of the ducts does not ap- 
pear to be complicated. 
* De glandularum secernentium penitiori struc- 
tara, p. 5 tab. v. fig. 6 and 7. 
LACRYMAL ORGANS. 
In reptiles the glandule of Harder is smal 
than the lacrymal gland. = 
The secretion of the glandule of Harder 
thick transparent viscid matter. . 
Ill. reting and derivative laer. 
anpatuia Tia Gevdocaae of the laer 
gland and of that of Harder is generally m 
inverse ratio. It would appear that the ¢ 
9 
tive lacrymal apparatus is more in relation 
the lacrymal gland than with the glandt 
Harder, as it is much develo in man 
whom there is no glandule of Harder, and, 
reported, it is wanting in the elephant, in y 
the glandule of Harder is said to be 
large. The lacrymal gland exists in man, 
sapajous, and snakes, but no glandul 
Harder. In all other mammifera there is 
a lacrymal gland and a glandule of Hai 
proportion as the latter enlarges the forme: 
comes smaller. Among the cetacea, the 
phin possesses a lacrymal gland which 
rounds the eyeball likea ring. Its exer 
ducts, which are numerous, open on the’ 
surface of both upper and lower eyelids. 
derivative lacrymal apparatus is wantin 
this respect, seals and walrusses agree wit 
cetacea.* Other mammals, as moles and s 
mice, are said to present no trace of laet 
apparatus. In the elephant, small gl 
grains the size of a are said to represen 
lacrymal gland. Camper says the hip 
tamus has no puncta, from which mi 
ferred the absence of any lacrymal passage 
the nose. The elephant is also said to 
the derivative lacrymal apparatus. “s 
In birds the lacrymal gland is small, at 
at the posterior angle of the eye, either to 
the roof or the floor of the orbit. The der 
lacrymal organs in the common fowl, — 
stance, consist of two large lacrymal p 
upper the larger, and a membraneous 
leading into the nose. = 
In reptiles, the lacrymal gland lies behin 
eyeball, and is of considerable size, espec 
in harmless serpents. According to Duve 
the lacrymal gland in one species of ty; 
is six times larger than the extremely di 
tive eyeball; but even in rg 
the viper for instance, it is large. 
The sauria and chelonia have for th 
part both a lacrymal gland and a glan¢ 
Harder, the former the larger. Batrachia 
the lacrymal apparatus. 
In serpents the secretion of the lac 
gland is poured into the oculo-palpebi al 
from which a lacrymal duct leads. — 
colubri there is, in the fore and lowe 
the oculo-palpebral space, a hole © 
pore, in some individuals seen with di 
very distinct on the con in @ 
which may admit a bristle. is is th 
mal point; it is single and is continue 
a very slender membranous duct, 
tet pg which forms the lacrymal 
is, in harmless serpents, opens into @ 
pouch commaniodtiaged with the mouth im 
* Rapp. l.c. Rapp describes, in the t 
scattered grains of lacrymal gland, which 
the conjunctiva near the eyeball. ‘ 
a 
. 
= 
