LACRYMAL ORGANS. 



83 



These are elongated more or less compound 

 follicles, secreting a peculiar sebaceous matter 

 intended as an ointment to protect the delicate 

 integument of the margins of the eyelids from 

 any irritation which might result from friction, 

 or the frequent contact of the tears, and also to 

 preserve to it that peculiar degree of sensibility 

 which, like all other transition structures from 

 skin to mucous membrane, it possesses. The 

 Meibomian glands lie imbedded in the sub- 

 stance of the tarsal cartilages. They are ar- 

 ranged close and parallel to each other, and ge- 

 nerally speaking in a direction at right angles to 

 the ciliary margin of the eyelids, where they open 

 in that row of minute apertures already mention- 

 ed. There are between thirty and forty Meibomian 

 glands in the upper eyelid, but not so many in 

 the lower, in which also they are shorter in 

 consequence of the difference in breadth be- 

 tween the upper and lower tarsus. Sometimes 

 two glands are united towards their orifice ; 

 sometimes, on the other hand, at their end. 

 Frequently the tail of the gland bends laterally 

 and describes an arch. The structure of the 

 Meibomian glands consists essentially in a 

 central canal running from one extremity to the 

 other, like the duct of the pancreas, and around 

 that canal glandular loculi or cryptae opening 

 into it directly, or through the medium of each 

 other. The duct suddenly contracts before 

 opening on the margin of the eyelid. In a 

 transverse section of the Meibomian glands this 

 canal is seen, according to Zeiss, as a small 

 hole around which are placed from five to six 

 glandular grains. 



The Meibomian glands of the sow are small ; 

 representing merely a short cyst subdivided 

 into several loculi. The glands of the eye- 

 lashes in the same animal are, on the contrary, 

 large. The Meibomian glands of the sheep, 

 dog, and fox, are long very thick-walled bodies, 

 in the middle of which there is a wide canal. 

 Ranking next in complexity of structure are 

 the human Meibomian glands. Those of the 

 horse, ox, goat, and cat, Zeiss found still more 

 complex, consisting of lobes, lobules, and 

 granules.* 



The secretion of the Meibomian glands is a 

 mild, yellowish, unctuous substance, of the 

 consistence of lard. Occasionally the external 

 orifice of one or more of the Meibomian ducts 

 becomes covered by a thin film, apparently of 

 epidermis. This prevents the escape of the 

 secretion, which accumulating raises up the 

 film into a small elevation, like a phlyctenula. 

 This does not actually cause pain, but gives 

 rise to uneasiness in the part when the eyelids 

 are moved : the film is easily broken, and the 

 accumulated secretion removed on the point of 

 a pin. 



Hordeolum, or stye, according to some, is 

 abscess of the Meibomian glands ; according 

 to others, a small boil implicating the cellular 

 tissue at the margin of the eyelid. Zeissf sus- 

 pects it has its seat in the capsule and glands 



* Zeiss's papers in Ammon's Zeitschrift, B. iv. 

 and v., already quoted, 

 t Locis citatis. 



of the roots of the eyelashes. Abscess of the 

 Meibomian glands does occur, and gives rise 

 to a tumour on the edge of the eyelid like a 

 stye, but the nature of the case is seen on 

 everting the eyelid. There can be no doubt 

 that the roots of the eyelashes are involved in 

 the disease, because the hairs at the part affect- 

 ed generally fall out at the end. Dr. Zeiss 

 proposes to anticipate this result by plucking 

 them out at once, and he says that by this pro- 

 cedure the progress of the complaint is arrested, 

 a thing, certainly, occasionally very desirable. 

 In a small inflammatory tumour at the root of 

 a hair on the cheek, I have obtained such a 

 result from plucking out the hair. 



Fig. 12. 



The eyelids of the right side seen from within. 

 ( Modified from Soemmerring.) 



a, a, Inner surface of orbicularis palpebrarum 

 muscle. 



b, Palpebral fissure. 



c, c, c, Upper mass of lacrymal gland. 



d, Lower mass of lacrymal gland. 



e, e, Conjunctiva. The palpebral portion is 

 smoothly spread on the inner surface of the eyelids. 

 The portion which has been dissected from off the 

 eyeball is in folds. 



f, Hairs inserted into the orifices of the ducts of 

 the lacrymal gland. These orifices are on the 

 conjunctival surface of the upper eyelids towards 

 its temporal extremity. 



g, g, Meibomian glands of both eyelids seen 

 shining through the conjunctiva and the thin layer 

 of tarsal cartilage covering them on the inside of 

 the eyelids. 



h, Lacrymal papilla and point of the upper 

 eyelid. 



', The same of the lower eyelid. 

 k, Lacrymal caruncle. 



I, Semilunar fold pressed aside to show the 

 caruncle. 



II. The conjunctiva, semilunar fold, and 

 lacrymal caruncle. 



The conjunctiva in general. Tunica con- 

 junctiva seu adnata. Fr. La Conjunctive. 

 Ital. La Congiuntiva. Germ. Die Bind/uiut. 

 The conjunctiva is that membrane which lines 

 the posterior surface of the eyelids, and covers 

 the front of the eyeball to the extent of about a 

 third of its whole periphery. This disposition 

 has given rise to the distinction of a palpebral 

 and ocular conjunctiva. Towards the margin 

 of the orbit, all round the circumference of the 

 eyeball, a cul-de-sac is formed by the reflection 



G 2 



