242 Life and Health 



By it we are enabled to estimate differences of weight. If 

 an attempt be made to raise this object, it offers resistance, 

 which the muscles must overcome. The feeling of effort 

 accompanying an action is known as the muscular sense. It 

 depends on sensory nerves in the muscles, which carry 

 impressions from them to the nerve centers. 

 ^ 374. Sense of Temperature. The skin also judges, to 

 a certain extent, of heat and cold. These sensations can be 

 felt only by the skin and the mucous membrane at the 

 entrance to various passages. Direct irritation of a nerve 

 does not give rise to them. Thus, the exposed pulp of 

 a diseased tooth, when irritated by cold fluids, gives rise, 

 not to a sensation of heat or cold, but simply to pain. 

 Various portions of the body have different degrees of 

 sensibility. The hand will bear a degree of heat which 

 would cause pain to some other parts of the body. 

 i 375. Sense of Pain. The sense of pain is due to an 

 excessive stimulation of the sensory nerves, and in it all 

 finer sensations are lost. Thus, when a piece of hot iron 

 burns the hand, the sensation is the same as when the iron 

 is very cold. Extreme cold feels like intense heat. 

 J 376. The Tongue as an Organ of Taste. The sense of 

 taste is located chiefly in the tongue but may also be 

 referred even to the region of the fauces. Taste, like 

 touch, has its seat in special nerve endings. 



The tongue is a muscular organ, covered with mucous 

 membrane, and is richly supplied with blood vessels and 

 nerves. It is an important factor in chewing, in swallow- 

 ing, and in articulation. 



The surface of the tongue is nearly covered with irreg- 

 ular projections called filiform papillae, fine, thread-like 

 processes, about one-twelfth of an inch high. Interspersed 

 with these are the fungiform papillae. These are shaped 



