SENSITIVE SYSTEM. 373 



fined in its situation. It is a pale, yellowish, delicate mass, of 

 an irregular figure, moderately convex superiorly, in accommoda- 

 tion to the bone, inclining to the concave inferiorly, to adapt it to 

 the globe, of whose upper and outer surface it occupies the sum- 

 mit. Its thickest and broadest part is turned forward; it grows 

 thin and narrow behind. It is a gland of the conglomerate class, 

 being constituted of many lobules, resembling externally those of 

 the salivary glands, connected together by a delicate and easily 

 lacerable cellular tissue. These lobules are themselves com- 

 posed of granules, which receive the terminating ramifications 

 of the supplying arteries. From the granules spring the radicles 

 of the excretory ducts, and they, by their inter-union with one 

 another, form a set of tubes that open upon the surface of the 

 conjunctiva lining the upper lid, not far from the superior angle, 

 by seven distinctly visible orifices, large enough to admit an eye- 

 probe, whose margins are marked by slight eminences upon the 

 smooth plane of the membrane. The office of this gland is to se- 

 crete the tears; and they are conveyed and poured by its ducts 

 upon the surface of the conjunctiva, where they become diffused, 

 partly by their own weight and partly by the motion of the lids, 

 over the transparent part of the eye. The tears consist of a wa- 

 tery fluid, possessing a brackish flavour, from some saline im- 

 pregnations they contain, and from the same cause having slight- 

 ly irritating properties ; so that, when long or often discharged 

 upon any undefended part, they are very apt to occasion excoria- 

 tion. 



Caruucula Lachrymalis. 



The lachrymal caruncle is a little black or pied tuber- 

 cle, whose magnitude varies somewhat in difl^erent horses, lodged 

 within the inferior canthus, in the vacancy between the eyelids 

 and the eyeball. Only that part of it is black or pied, however, 

 which is visible without disturbing the lids ; and this is owing 

 to a covering it receives from the skin, which turns in for that 

 purpose at the canthus; for its base is clothed by conjunctiva, 

 the membrane being continuous with the cuticular covering. 

 From its cuticular surface grow several very fine, short hairs. 

 In the human subject, the caruncle is said to be glandular in its 

 composition, being constituted, it is asserted, of a structure 

 which may be resolved into mucous follicles: be this the fact or 

 not, in the horse it is found to yield a mucous matter by expres- 

 sion after death, and it is not uncommon, during life, to find a 

 little mucus collected within the canthus. It appears to serve 

 the mechanical purpose of directing the tears into the puncta 

 lachrymalia as they flow against it along the triangular canal*. 



* The caruncle is a little bit of fat rising up to fill an apparent vacancy. 

 It was thought to be an organ of secretion ; but we have now reason to 



