THE SPECIAL SENSES. 185 



these objects; such as size, figure, solidity, motion, and 

 smoothness or roughness of surface. 



22. The sense of touch assists the other senses, especially 

 that of sight, giving foundation and reality to their per- 

 ceptions. Without it, the impressions received by the eye 

 would be as vague and unreal as the figures that float 

 through our dreams. A boy who had been blind from 

 birth, at the age of twelve years received sight by means 

 of a surgical operation : at first, he was unable to distinguish 

 between a globe and a circular card, of the same color, be- 

 fore he had touched them. After that, he at once recog- 

 nized the difference in their form. He knew the peculiari- 

 ties of a dog and a cat by feeling, but not by sight, until 

 one day, happening to take up the cat, he recognized the 

 connection of, the two sorts of impressions, those of touch 

 and sight ; and then, putting the cat down, he said : " So, 

 puss, I shall know you next time." 



23. Touch is considered the least liable to error of all 

 the senses ; yet, if that part of the skin by which the sense 

 is exercised is removed from its customary position, a false 



Fro. 45. 



impression may be created in the mind. This is well il- 

 lustrated by an experiment, which dates from the time of 

 Aristotle. If we cross the middle finger behind the fore- 



22. Importance of the sense of touch to the development of the other senses? 



23. Liability of touch to err? Describe the illustration. 



