398 A YEAR IN SCIENCE 



of the body can be determined by the use of a compass.. 

 If the person operated upon has his eyes closed and 

 the compass is placed on the back of the neck with the 

 points three inches apart, he will get a distinct impres- 

 sion of each. If, however, the points are placed from 

 one and a half inches to two inches apart, he wdll feel 

 only a single point. On the tip of the tongue the two 

 points can be distinguished when separated only one 

 twenty-fourth of an inch. The lips and finger tips are 

 also very keen. When an object touches the skin the 

 pressure upon the touch corpuscles stimulates the nerve 

 endings and an impulse is sent to the brain. 



Temperature. It seems safe to assume that the 

 nerves which receive the impression of heat and cold 

 are not the same as those used for touch. When the 

 skin is touched with a cold object, certain areas all 

 over the body give us a sensation of cold. Other areas 

 when touched with a warm object give the sensation 

 of warmth. The body seems to be mapped out into 

 irregular "cold and warm" spots. 



Taste. The nerves of taste end in taste buds which 

 are in papillae scattered over the upper surface and 

 sides of the tongue, the pharynx, and in parts of the 

 soft palate. Hair-like processes project from the taste 

 cells through cavities in the taste buds. These proc- 

 esses come in contact with the food which must be in 

 solution to be tasted. 



There are four different kinds of tastes : sweet, sour, 

 bitter, and salt. All parts of the tongue are not equally 



