SUGGESTIONS FOR LABORATORY WORK 603 



SMELL 



Fatigue. With one nostril stopped, smell tincture of iodine 

 through the other. Hold the bottle near the nose, inhale evenly 

 and somewhat rapidly, and exhale through the mouth. 



Note the time required to produce exhaustion. 



Allow a minute for recuperation and repeat the above test. 

 Repeat until a minute does not suffice for recuperation. 



Note the successive exhaustion times. 



This experiment explains failure to perceive closeness in a room 

 through fatigue of the sense of smell. 



VISION 



A good introduction to the study of vision is the dissection of 

 the eye. 



Sheep's eyes hardened in formalin are satisfactory. Directions 

 for dissection are given below. 



Conjunctiva. This is the smooth membrane which is loosely 

 attached to the eye in front. It lines the lids, and is reflected 

 from the lid upon the surface of the ball. 



Muscles. Remove the fat which is adherent to the ball, so that 

 the external smooth coat will be exposed. The cut ends of several 

 muscles will be seen. 



The Cornea and Sclera. On the free surface of the ball the 

 elliptical area includes the cornea, transparent during life but 

 rendered opaque during preservation; the rest of the surface of 

 the ball is constituted by the naturally white and opaque sclera, 

 commonly called the sclerotic coat. 



Optic Nerve. With the finger and forceps tear apart the muscu- 

 lar masses surrounding the optic nerve, and remove with the 

 scissors. Notice the fibrous constitution of the nerve and the firm- 

 ness of the sheath ; also, that the nerve does not enter the center of 

 the eye. 



Aqueous Humor. Press the eye so as to make the cornea tense. 

 Cut through the cornea with the point of the scalpel; a clear fluid 

 will ooze out. 



Iris and Pupil. Raise the cut edge of the cornea with the forceps 

 and remove it with the scissors; a dark lamina, the iris, with a 

 central orifice, the pupil, will be seen. 



