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A MANUAL OF PHYSIOLOGY 



through a short-circuiting key with the secondary. Etherize a cat 

 by putting it into a large vessel with a lid, slipping into the vessel a 

 piece of cotton-wool soaked with ether, and waiting till the move- 

 ments of the animal inside the vessel have ceased. Then quickly 

 put the cat on a holder and maintain anaesthesia with ether. Expose 

 the sympathetic in the neck (p. 190); the carotid is taken as the 

 guide to it. Ligature the nerve, and cut below the ligature. On 

 stimulating the upper (cephalic) end, the pupil of the corresponding 

 eye dilates. 



FIG. 334. APPARATUS FOR COLOUR-MIXING. 



(b) Observe in the eye of a fellow-student, or, by means of a 

 looking-glass, in your own eye, that when light falls on one eye both 

 pupils contract. 



(c) Observe that when the eye is accommodated for a near object 

 the pupil contracts, and that it dilates when a distant object is 

 looked at. 



8. Colour-mixing. (a) Arrange a red and a bluish-green disc on 

 one of the steel discs of the colour-mixing apparatus shown in 



