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Show 170 EXPRESSION OF SUl!'FEUIN G : CHAl'. VI. to the Iacrymal glands. The. influence transmitt~d to these glands causes, as there IS good reason to behevo, the relaxation of the muscular coats of the smaller arteries · this allows more blood to permeate the ()'landul~r tissue and this induces a free secretion of tears. vVhen tl;e small arteries of the face, including those of the retina, are relaxed under very different circumstances, namely, during an intense blush, tho lacrymal glands are sometimes affected in a like 1nannor, for the eyes become suffused with tears. . It is difficult to conjecture how many reflex actions have originated, but, in relation to the presen~ c.ase. of the affection of the lacrymal glands through Hl'ltation of the surface of the eye, it n1ay be worth rBmarking that, as soon as some primordial forn1 became sen1iterrestrial in its habits, and was liable to get particles of dust into its eyes, if these were not washed out they would cause much irritation; and on the principle of the radiation of nerve-force to adjoining nerve-cells, the lacrymal glands would bo stimulated to secretion. As this would often recur, and as nerve-force readily passes along accustomed channels, a slight irritation would ultimately suffice to cause a free secretion of tears. As soon as by this, or by some other means, a reflex action of this nature had been established ana rend red easy, other stimulants applied to the surfaeo of the eye-such as a cold wind, slow inflammatory action, or a blow on the eyelids-would cause a copion~ Recrotion of tears, as we l\:now to be the case. The glands: nre also excited into action through the irritation of adjoining parts. Thus when the nostrils are irritatorl by pungent vapours, though the eyelids n1ay bo kept firmly closed, tears are copiously secreted; and this likewise follows from a blow on the nose, for instance from a CHAP. VI. \VEEPING. 171 boxing-glove. A stinging switch on tho fa o Jroduce , ns I have seen, tho same effect. In these latter ca ·e. tho I cretion of tears is an incidental r suit, ana f 110 direct service. .As all those parts of the fa c, including tho lacrymal gland,, are supplied with branches of th same nerve, namely, tho fifth, it is in some degree intelligible that tho effects of the excitement of any mw branch should spread to tho nerve-cells or roots of tho other branches. The internal part· of the oyo likowi ·e act, under c rtain conditions, in a reflex manner on the lacry1nal glands. The following Rtatements have been kindlv comn1unicated to 1n by Mr. Bowman; but tho subj ~t is a very intricate one, as all the part of the eye are so intimately related together, and are so sensitive t various stimulants. A strong light acting on the retina, wh n in a normal condition, has very little tendency to a use lacrymati?n; but with unhealthy childr n having sinall, old-standing ulcers on the corn a, the retina be(' Omes excessively sensitive to light, and exposure ov n to common daylight causes forcible and sustained closnr of tho lids, and a profuse flow of tear . Wh n persons who ought to begin the use of convex glasses habitually ~train the waning power of accominodation, an unduo P. cretion of tears very often follows, and tho retina i :-. liable to become unduly sen ·iti ve to light. In g neral, 111 rbid affections of the surface of tho ye, and of th0 iliary 1 tructuros concerned in the accomm dative a t. are prone to be accompanied with exc ssive s ·retion of' tears. Hardness of the eyeball, not ri ing to inflaminati n, but implying a want of balance betwo n tho flni<l. p ur d out (; nd again taken up Ly tho intra- nlar v I sels, is not u ually att nded with any la rynw,ti n. "\Vhen the balance is on the other side, and th' y l con1es too . oft, there is a greater t ndoncy to la ry- |