THE EYE. 331 



mind, called sensation, is effected. The organs of sense are 

 divided into external and internal. The former comprise 

 the eye, the ear, the tongue, the nose, and the skin, per- 

 forming the functions of seeing, hearing, tasting, smell- 

 ing, and touch. The latter division of internal sensation 

 includes the brain and nervous system. 



SECTION I. 



THE EYE. 



The organ of vision consists of the eye proper or ball, 

 and of the appendages of the eye, or tutamina oculi. 



The ball or globe of the eye furnishes an example of the 

 most perfect of optic instruments, and the most surprising 

 adaptation in all its parts, for the purposes of vision. It, in 

 fact, combines the properties of both the microscope and 

 telescope, being constructed to view objects both near and 

 at a distance, and having special relation to the stimulus 

 of light. , 



The eye is situated in front of the bony orbit resting 

 upon an elastic cushion of fat, which allows it great mo- 

 bility, and which, from its quantity, whether great or 

 small, will Cause a proportionate projection or retraction ; 

 so as to give the appearance of either large or small 

 eyes, though, in fact, the eye may not vary absolutely 

 in size. 



It is surrounded and retained in its situation by muscles, 

 vessels, nerves, the conjunctive membrane and the eyelids. 

 Its form is nearly a sphere; the antero-posterior diameter 

 being somewhat the longest on account of the projection 



and the other is connected with the otic ganglion and with Jacobson's nerve. 

 Regarding this ganglion as a nervous centre, then, we have, entering into it, 

 filaments from the seventh, eighth, fifth, and sympathetic nerves. The chorda 

 tympani springs from it, crosses the tympanum, as already described, lies close 

 to the gustatory, and finally is, according to some anatomists, distributed to the 

 lingualis muscle ; according to others, connected with the submaxillary gan- 

 glion. We have already alluded to this complex relationship, and have called 

 attention to the opinion of Malaguti, that this portio intermedia is a sympathetic 

 nerve, entering the substance of the brain, and uniting a very great diversity 

 of organs by its numerous connections. 



