188 THE SPECIAL SENSES. 



very cold substance causes pain, not the feeling of cold. 

 So that a red-hot iron, and solid carbonic acid (the tem- 

 perature of which is 108 below zero), feel alike ; and each, 

 if pressed slightly, will produce a blister. 



28. The muscular sense, by some considered distinct 

 from touch, gives rise to the sensations of weight, and 

 other forms of external resistance. That this feeling 

 exists, is shown by the following simple experiment. If 

 the hand be placed flat upon a table, and a somewhat 

 heavy weight be put into it, touch alone is exercised 

 and a feeling of pressure results; but if the hand be 

 raised, a certain amount of muscular effort must be put 

 forth, and thus the sensation of weight is recognized. 

 Through the muscular sense, precision of effort is rendered 

 possible ; for by it we learn to adjust the force exerted to 

 the weight of the object to be lifted, moved, or carried. 

 Without it, all our movements would necessarily become 

 ill-regulated and spasmodic. In cases of disease, where the 

 sensibility of the lower limbs is lost, while power of motion 

 remains, the patient is able to stand erect so long as he 

 can see his limbs; but just as soon as his eyes are closed, 

 he begins to waver, and will fall unless supported. 



29. The Organ of Taste. The tongue is the special 

 organ of the sense of taste ; but the back part of the mouth 

 also possesses this faculty. The tongue is a muscular 

 organ, the muscles composing it being so numerous and 

 interwoven as to give it the freedom and variety of motion 

 which it possesses. It can curve itself upward or down- 

 ward; it can extend or contract itself; and, with its point, 

 can sweep the cavity of the mouth, in all directions, in 

 the search for scattered particles of food. 



30. The upper surface of the tongue is peculiar, being 

 marked by the presence of innumerable paptffo, some of 



28. The muscular sense ? State what is paid to illustrate the subject. 



29. The or<ran of taste ? The tonprne ? Its powers of motion ? 

 ftO. Peculiarities of the tongue ? Uses of the papillae ? 



