BODY CONTROL AND HABIT FORMATION 361 



accounts for the black appearance of the pupil of the eye, when we look 

 through the pupil into the darkened space within the eyeball. The 

 retina acts as the sensitized plate in the camera, for on it are received the 

 impressions which are transformed and sent to the brain as sensations of 

 sight. The eye, like the camera, has a lens. This lens is formed of 

 transparent, elastic material. It is found directly behind the iris and is 

 attached to the choroid coat by means of delicate ligaments. In front of 

 the lens is a small cavity filled with a watery fluid, the aqueous humor, 

 while behind it is the main cavity of the eye, filled with a transparent, 

 almost jelly like, vitreous hujnor. The lens itself is elastic. This circum- 

 stance permits of a change of form and, in consequence, a change of 

 focus upon the retina of the lens. By means of this change in form, or 

 accommodation, we are able to distinguish between near and distant 

 objects. 



Defects in the Eye. — • In some eyes, the lens is in focus for near objects, 

 but is not easily focused upon distant objects ; such an eye is said to be 

 nearsighted. Other ej^es 

 which do not focus clearly 

 on objects near at hand are 



said to be farsighted. Still ^^ ^ ,,,,.« 



. , How far away can you read these letters: 



another eye detect is astig- Measure the distance. Twenty feet is a 



matism, which causes images test for the normal eye. 



of lines in a certain direction 



to be indistinct, while images of lines transverse to the former are distinct. 

 Many nervous troubles, especially headaches, may be due to eye strain. 

 We should have our eyes examined from time to time, especially if we are 

 subject to headaches. 



The Alcohol Question. — It is agreed by investigators that in 

 large or continued amounts alcohol has a narcotic effect ; that it 

 first dulls or paralyzes the nerve centers which control our judg- 

 ment, and later acts upon the so-called motor centers, those which 

 control our muscular activities. 



The reason, then, that a man in the first stages of intoxication 

 talks rapidly and sometimes wittily, is because the centers of judg- 

 ment are paralyzed. This frees the speech centers from control 

 exercised by our judgment, with the resultant rapid and free flow 

 of speech. 



In small amounts alcohol is believed by some physiologists to 

 have always this same narcotic effect, while other physiologists 



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