92 CONSCIOUS NERVOUS OPE NATIONS 



33. The Epidermis. Observe that with a needle a portion of the 

 outer skin may be removed without pain or flow of blood. If the 

 hands be washed in warm water and then dried, on rubbing them 

 together briskly, portions of the dead scaly epidermis will be removed. 



On the palm of the hand the epidermis is seen to be thrown up in a 

 series of curved parallel ridges. The latter are caused by the projec- 

 tions of the papillae of the underlying dermis. On examination with 

 a lens, large numbers of the minute openings of the sweat glands may 

 be seen on the ridges of the epidermis. 



34. Discrimination in Touch. Find the least distance at which the 

 points of a pair of blunt-pointed compasses can be distinguished as 

 two points when applied to the skin of the arm. Repeat the same 

 experiment on the back of the hand, the forehead, the finger tips, and 

 the tip of the tongue. In this way a region of greatest sensitiveness 

 can be distinguished. 



35. Location of Touch. Ask a person to close his eyes, touch some 

 part of his body with a pencil, and ask him to indicate the same point 

 with another pencil, immediately afterward. He will probably make 

 some errors. The experiment may be made more interesting by repeat- 

 ing the trials, taking the measure of each error and averaging the 

 errors. By repeating this experiment on a number of persons, some 

 very interesting results may be obtained and tabulated. 



36. Aristotle's Experiment. Cross the middle over the index finger 

 so that the tip of the middle finger is on the thumb side of the index 

 finger. Place between the two a marble or other small object. A 

 sensation of two objects will result, especially if the fingers be moved. 



37. Delicacy of Touch. With small weights of pith or cork, find 

 the least pressure that is perceptible on the skin of the arm and tips 

 of fingers. The weights may be applied by lowering them upon the 

 skin by means of delicate silk fibers attached to them. The surface 

 which is applied to the skin should have the same area in all the 

 weights, and care should be taken that the weights do not move after 

 touching the skin. The person experimented upon should keep the 

 eyes closed while the weights are being applied. The weights should 

 also be applied to the forehead, temples, lips, and tongue. The main 

 purpose of this experiment is to determine the regions of the skin 

 most sensitive to contact. 



38. Hairs as Organs of Touch. If the weights used in the preced- 

 ing experiment be applied to regions of the skin possessing hairs, it 



