35.3 



CHAPTER VIII. 



THE SECRETIONS OF THE LACHRYMAL, MEIBOMIAN, AND 

 CERUMINOUS GLANDS. 



The Tears. 



THE glandulse lachrymales are two conglomerate acinous 

 glands which secrete a limpid fluid, containing a very small 

 proportion of solid constituents, and forming the tears. They 

 are for the purpose of preserving the cornea of the eye in a 

 state of moisture, and their secretion is much increased by in- 

 tense feelings either of joy or grief. 



The tears have not yet been subjected to an accurate analysis, 

 partly perhaps from the subject being one of little interest in 

 a scientific point, and partly from the difficulty of obtaining a 

 sufficient quantity. 



When examined under the microscope, the tears exhibit a 

 small quantity of pavement epithelium and a few mucus-cor- 

 puscles swimming in a clear fluid. They have a slightly saline 

 taste, (much like that of the perspiration that exudes from the 

 forehead,) and change red litmus-paper to a pale blue. 



The only chemical examination of the tears that can be de- 

 pended on is that of Fourcroy and Vauquelin, who assert that 

 they resemble in their constitution the aqueous humour of the 

 eye. The solid constituents amount to only Ig, and consist prin- 

 cipally of chloride of sodium and of a yellow extractive matter 

 which is not perfectly soluble in water : it is not improbable 

 that the insoluble portion arises from the fatty-mucous secretion 

 of the meibomian glands. The mucus also into which, accord- 

 ing to those chemists, the extractive matter of the tears is con- 

 verted previously to its being perfectly dried, may be, as Ber- 

 zelius conjectures, the secretion of the meibomian glands. With 

 regard to this latter secretion, the gummy secretion of the 

 eyes, we know even less than of the tears : it seems to consist 

 principally of a mucous matter and of fat. 



ii. 23 



