LACRYMAL ORGANS. 



89 



sion of a size sufficient to receive the point 

 of the thumb, situated in the roof of the 

 orbit at its upper and outer angle, just 

 within the overhanging outer extremity of 

 the superciliary arch. The superior lacrymal 

 gland is of an oval or triangular shape about 

 three-fourths of an inch in its longest diameter 

 and about half an inch across. It is flattened 

 from above downwards. Its upper surface is 

 convex ; its lower plane or concave. The 

 thickest edge of the gland is turned outwards. 

 The gland is of a reddish colour and is en- 

 veloped in a thin but dense cellular coat. The 

 lower mass of the lacrymal gland, or glandula 

 lacrymalis inferior, is a loosely connected ag- 

 gregation of lobules of the same glandular 

 substance as the above. It was first described 

 by the second Monro, who called the lobules, 

 for distinction's sake, glandula congregate* 



The lower mass of the lacrymal gland is 

 smaller than the upper, with which it is in con- 

 tact above, whilst below it extends to the outer 

 part of the upper margin of the tarsal cartilage of 

 the upper eyelid. It lies indeed in the substance 

 of the upper eyelid at the outer part. It is seen 

 shining through the conjunctiva in everting the 

 upper eyelid. 



Fig. 13. 



Lacrymal gland, left side. 



a a, Superior mass ; b b, inferior mass ; c, part 

 of inferior mass lying towards the outer canthus. 



Intimate structure of the lacrymal gland. 

 The lacrymal gland is what is commonly called 

 conglomerate. It belongs to Muller's com- 

 pound glands with canals of the ramified type. 

 "In the arrangement of the secreting canals 

 of the lacrymal glands," says Miilleryf " two 

 principal forms are observed : the one is that 

 which I discovered in the chelonian reptiles ; 

 the other, that which prevails in birds and 

 Mammalia. In the chelonia, the gland is 

 formed of a number of club-shaped lobes, 

 united together by means of the different ducts 

 which run in their interior. The duct of each 

 lobe is pretty uniform in diameter, and into it 

 open an innumerable quantity of microscopical 

 tufts of coeca, which are arranged around it 



* Monro's Observations, Anatomical and Phy- 

 siologicul, wherein Dr. Hunter's claim to some dis- 

 coveries is examined, p. 77. Edinburgh, p. 77. 

 Rosenmuller, Partium Externarum oculi humani, 

 imprimis organorum lacrymalium descriptio anato- 

 mica, &c. 109. Lipsia:, 1810. 



t Handbuch der Physiologic des Menschen, 

 Bd. i. S. 438. Or, Translation by Baly, p. 445. 

 See also " De glandularum secernenticun penitiori 

 structura, p. 51, 52, tab. v. figs. 3, 4, 5, & 8. 



at right angles like the foliage of a moss on its 

 stem." In birds, in which the lacrymal gland 

 is very small and situate at the posterior angle 

 of the eye, and Mammalia, the secreting ca- 

 nals of the lacrymal gland are regularly 

 branched and terminate in each acinus in a 

 number of small cells. In birds these cells 

 are very large ; and in them, and likewise in 

 the horse, the cells can be filled with mercury 

 from the efferent duct. 



Efferent or excretory ducts of the lacrymal 

 glands. The lacrymal glands pour out their 

 secretion by nine or twelve very slender excre- 

 tory ducts which proceed from above down- 

 wards and open on the surface of the con- 

 junctiva on the inside of the upper eyelid. 

 The orifices of the ducts are placed at about 

 one-twentieth of an inch apart from each other 

 in a row extending about half an inch from the 

 outer canthus inwards, parallel to but a little 

 above the outer part of the upper margin of 

 the tarsal cartilage, that is, at the inferior boun- 

 dary of the lower mass of the gland. 



The excretory ducts of the lacrymal gland 

 were first discovered on the llth of November, 

 1665, by Nicolaus Steno,* in the eyelid of a 

 sheep. He delineated them from the eye of 

 the calf. Moreover it appears that Steno de- 

 scribes vasa lacrymalia discovered in man, 

 which opened in the membrane of the upper 

 eyelid.f 



Admitted by some and doubted by others 

 from the time of Steno, the ducts of the lacry- 

 mal gland became a subject of dispute between 

 Dr. William HunterJ and the second Monro, 

 the one claiming to have observed them in the 

 human eye before the other. 



The best way to demonstrate the ducts is to 

 stretch the upper eyelid, turned inside out, 

 upon the finger ; then wipe clean the surface 

 of the conjunctiva, and having by close in- 

 spection at the place where the ducts open, 

 as above described, discovered the orifices, 

 take a short piece of human hair in the point 

 of a forceps, and entering it at the orifice, 

 push it on in the direction of the duct. From 

 the orifices on the surface of the conjunctiva 

 the ducts run nearly parallel with each other 

 upwards. 



Of two eyes before me I have in this way 

 inserted hairs into nine orifices of ducts in the 

 one and into twelve orifices of the other, a 

 work which did not occupy five minutes for 

 each eye. In both eyes there is one orifice of 

 a duct exactly within the external commissure, 



* Observationes Anatomicae, quibus varia oris, 

 oculorum et narium vasa describuntur, novique 

 salivas, lacrumarum et muci fontes deteguntur et 

 novum Bilsii commentum rejicitur. Leidae, 1662. 

 See also Bibl. Anat. Clerici et Mangeti. Genev. 

 1699. fol. torn. ii. p. 787. 



t Thorn. Bartholoni epistolarum medicinalium a 

 doctis et ad doctos scriptarum centuria iii. & iv. 

 Hafniae, 1667-8. Epist. 53. cent. iv. 



$ Monro's Observations, Anatomical and Phy- 

 siological, wherein Dr. Hunter's claim to some 

 discoveries is examined, p. 77. Edinburgh, 1758. 



Dr. William Hunter's Medical Commentaries, 

 p. 1, containing a plain answer to Professor Monro. 

 London, 1762-4. 



