TOUCH. 



297 



disc to effect the same result, 

 cage to keep it from moving. 

 A very suitable one was 

 devised by Michel, use it. 

 (Fig. 141.) Examine the 

 eye by the direct and indi- 

 rect methods already de- 

 scribed. N. B. If an albino 

 rabbit be used, the observer 

 sees the large choroidal 

 vessels. 



4. Perrin's Artificial Eye. 



Place the rabbit in a suitable 



Fig. 141. Carriage for Rabbit. 



(a.) Use this until a clear image of the fundus is obtained 

 by both methods. In fact, it is well for the student to 

 begin with this. In this model eye-caps to fit on to the eye 

 are supplied, so as to render the eye-model either myopic or 

 hypermetropic. Afterwards test these, and use the necessary 

 lenses behind the mirror to correct these errors in the shape 

 of the eyeball. 



5. Kiihne's Method. If an artificial eye is not at hand, a very 

 suitable arrangement is that devised by Kiihne. Paint a disc 

 to resemble the normal fundus when it is seen with the ophthal- 

 moscope. Remove the eye-piece long one from an ordinary 

 microscope. Screw out the lower lens of the eye-piece, fix in 

 the painted disc, and block up the lower aperture with a piece 

 of cork. Fix the eye-piece in a suitable holder, and use it 

 instead of an eye to be examined. 



LESSON LXV. 



TOUGH SMELL TASTE HEARING. 

 1. Touch. The Sense of Locality. 



(a.) Cause a person to shut his eyes, touch some part of 

 his body with a pin, and ask him to indicate the part 

 touched. 



