210 THE HUMAN BODY 



curved hairs, arranged in one or two rows along each lid where 

 the skin joins the conjunctiva. 



The Lachrymal Apparatus consists of the tear-gland in each 

 orbit, the ducts which carry its secretion to the upper eyelid, 

 and the canals by which the tears, unless when excessive, are 

 carried off from the front of the eye without running down over 

 the face. The lachrymal or tear-gland, about the size of an almond, 

 lies in the upper and outer part of the orbit, near the front end. 

 It is a compound racemose gland, (see Chap. XXIX) from which 

 twelve or fourteen ducts run and open in a row at the outer corner 

 of the upper eyelid. The secretion there poured out, is spread 

 evenly over the exposed part of the eye by the movements of 

 winking, and keeps it moist; finally the tear is drained off by two 

 lachrymal canals, one of which opens by a small pore (punctum 

 lachrymalis) on each lachrymal papilla. The aperture of the lower 

 canal can be readily seen by examining the corresponding papilla 

 by the aid of a looking-glass. The canals run inwards and open 

 into the lachrymal sac, which lies just outside the nose, in a hollow 

 where the lachrymal and superior maxillary bones (L and MX, 

 Fig. 28) meet. From the sac the nasal duct proceeds to open into 

 the nose-chamber, below the inferior turbinate bone and within 

 the nostril. 



Tears are constantly being secreted, but ordinarily in such 

 quantity as to be drained off into the nose, from which they flow 

 into the pharynx and are swallowed. When the lachrymal ducts 

 are stopped up, however, their continual presence makes itself 

 unpleasantly felt, and may need the aid of a surgeon to clear the 

 passage. In weeping the secretion is increased, and then not only 

 more of it enters the nose, but some flows down the cheeks. The 

 frequent swallowing movements of a crying child, sometimes 

 spoken of as " gulping down his passion, " are due to the need 

 of swallowing the extra tears which reach the pharynx. 



The Muscles of the Eye (Fig. 80). The eyeball is spheroidal 

 in form and attached behind to the optic nerve, n, somewhat as 

 a cherry might be to a thick stalk. On its exterior are inserted 

 the tendons of six muscles, four straight and two oblique. The 

 straight muscles lie, one (superior rectus), s, above, one (inferior 

 rectus), not appearing in the figure, below, one (external rectus), 

 a, outside, and one (internal rectus), i, inside the eyeball. Each 



