168 EXPRESSION OF SUFFERING: Chap. VI. 



and energetic contraction of the muscles round the eyes, 

 and the secretion of tears, cannot be positively ascer- 

 tained, but a probable view may be suggested. The 

 primary function of the secretion of tears, together with 

 some mucus, is to lubricate the surface of the eye; and 

 a secondary one, as some believe, is to keep the nostrils 

 damp, so that the inhaled air may be moist, 21 and like- 

 wise to favour the power of smelling. But another, and 

 at least equally important function of tears, is to wash 

 out particles of dust or other minute objects which may 

 get into the eyes. That this is of great importance is 

 clear from the cases in which the cornea has been ren- 

 dered opaque through inflammation, caused by particles 

 of dust not being removed, in consequence of the eye 

 and eyelid becoming immovable. 22 The secretion of 

 tears from the irritation of any foreign body in the eye 

 is a reflex action; — that is, the body irritates a peripheral 

 nerve which sends an impression to certain sensory 

 nerve-cells; these transmit an influence to other cells, 

 and these again to the lacrymal glands. The influence 

 transmitted to these glands causes, as there is good rea- 

 son to believe, the relaxation of the muscular coats of 

 the smaller arteries; this allows more blood to permeate 

 the glandular tissue, and this induces a free secretion of 

 tears. When the small arteries of the face, including 

 those of the retina, are relaxed under very different cir- 

 cumstances, namely, during an intense blush, the lacry- 

 mal glands are sometimes affected in a like manner, for 

 the eyes become suffused with tears. 



It is difficult to conjecture how many reflex actions 

 have originated, but, in relation to the present case of 



21 Bergeon, as quoted in the ' Journal of Anatomy and 

 Physiology,' Nov. 1871, p. 235. 



22 See, for instance, a case given by Sir Charles Bell, 

 ' Philosophical Transactions,' 1S23, p. 177. 



