Physiology : a manual for students and practitioners . e warning when any foreign substancegets in the eye. What is the lachrymal gland? Tt is a small racemose gland lodged in the upper and outer partof the orbit. It has several ducts, which lead to the surface ofthe conjunctiva of the upper lid. The secretion of the gland isusually just sufficient to keep the eye moist, but under the stimu-lus of pain or intense emotion the secretion is increased, and ap-pears in drops which flow from the eyes—tears. Under ordinarycircumstances a slight excess of this moisture is drained into the 11—Phy. 162
Physiology : a manual for students and practitioners . e warning when any foreign substancegets in the eye. What is the lachrymal gland? Tt is a small racemose gland lodged in the upper and outer partof the orbit. It has several ducts, which lead to the surface ofthe conjunctiva of the upper lid. The secretion of the gland isusually just sufficient to keep the eye moist, but under the stimu-lus of pain or intense emotion the secretion is increased, and ap-pears in drops which flow from the eyes—tears. Under ordinarycircumstances a slight excess of this moisture is drained into the 11—Phy. 162 THE SENSES. nasal cavity by the lachrymal duct. This secretion is slightlyalkaline, and contains about 1 per cent, of solids, chiefly sodiumchloride. What are the Meibomian glands ? They are a number of small racemose glands, lying beneath theconjunctiva, which secrete an oily protective substance. The ductsof these glands open along the edge of the lid. Describe the eyeball. It consists of a tough, opaque globe (Fig. 47), having a some- FiG. Horizontal Section of the Eight Eyeball: 1, optic nerve; 2, sclerotic coat; 3, cornea;4, canal of Schlemm; .5, choroid coat; 6, ciliary muscle; 7, iris; 8, crystalline lens;9, retina; 10, hyaloid membrane; 11, canal of Petit; 12, vitreous body. what more sharply-curved translucent portion, the cornea, at thefront. It has in the anterior portion a lens^ and in front andbehind this are chambers which contain fluids: the one in front is SIGHT. 163 [? the anterior chnmher, and contains the aqueous fluid, while theposterior is the vifreotts /iiniinr. These structures fill the eyeballand give it a tense feel to the touch. What are the coats of the eyeball ? (1) Tlu! .«/iiii. or sc/<rfic eodt, is external, and covers aboutlive-sixths of the globe. The cornea is continuous with it in is composed of tough white fibres arranged in interconinumi-catiug layers. (2) The choroid coat is very vascular, being com-posed of a mesh of c
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiology, bookyear1
