IN HYGIENIC PHYSIOLOGY. 201 



21. Why can an elderly person drink tea which to a 

 child would be unbearably hot ? 



The sensation of touch has become impaired, and is much 

 less delicate. 



22. IVJiy does an old man hold his paper so far from 

 his eyes ? 



"Far sight" is common among elderly people, and is reme- 

 died by convex glasses. In old age the power of adjusting the 

 crystalline lens is lost. 



23. Would you rather be punished on the tips of your 

 fingers than on the palm of your hand ? 



The sense of touch is much keener in the tips of the fingers 

 than in the palm of the hand. 



24. What is the object of the eyebrows ? Are the hairs 

 straight ? 



They serve to prevent the perspiration of the forehead from 

 running down into the eye. They act, in a measure, with the 

 eyelashes, also to screen the eye from the dust and glaring 

 light. The hairs of the eyebrows overlap each other, and are 

 set obliquely outward. 



25. What is the use of winking ? 



It serves to wash the eyeballs, and thus keep the "windows 

 of the soul" clean. The necessity for winking is shown by the 

 great effort required to restrain it even for a short time. First 

 discomfort, then congestion of the mucous membrane, and then 

 a profuse watering of the eye follow any attempt at stop- 

 ping this necessary act. It is an obscure sense of discomfort, 

 not usually noticed by the consciousness, that excites this move- 

 ment, the objects of which are periodically to cleanse the ex- 

 posed, part of the eyeball, to moisten and lubricate it with the 

 secretions from the neighboring glands, and probably in this 

 way to aid in the preservation of the polish and translucency 

 of the epithelial layer on the transparent portion of the globe. 

 At the same time it carries toward the inner corner all for- 

 eign bodies, and directs the residual secretions toward the 



