284 PHYSIOLOGY. 



Heat or cold, if applied directly to a nerve trunk, does not 

 rouse sensations of temperature, but, if strong enough, 

 produces pain. If the elbow be dipped into water at the 

 freezing point, a sensation not of cold but of pain is caused, 

 and is felt in the hand. Heat and cold are not felt in the 

 digestive tube except at or near the openings. If very hot 

 liquid be swallowed, it may cause pain in the gullet and 

 stomach. If a considerable quantity of warm liquid be 

 taken, it may give a feeling of warmth from its effect on 

 the skin of the abdomen, by conduction of heat outward. 

 As with other senses, a sudden change in the degree of 

 the stimulus is more certain to rouse sensation than a 

 gradual change. 



READING. The Five Senses of Man, Bernstein. 



* Summary. i. The cutaneous sensations are touch proper, tem- 

 perature sense, and pain. 



2. There are touch corpuscles in the papillae of the dermis. 



3. Touch is the most general of the senses, both in its extent in our 

 bodies, and in the number of animals possessing it. 



4. Touch proper, or pressure sense, is tested by discrimination of 

 additional pressure. 



5. Touch localization is tested by discrimination as to the distance 

 of two points of contact. 



6. Temperature is discerned by a special set of nerve fibers. 



7. Touch and muscular sense are necessary adjuncts of sight to give 

 correct perceptions of size and form. 



Questions. i . What is the explanation of tickling ? 



2. Where does the change occur by which we become more dis- 

 criminating in the sense of touch ? 



3. Why does an emotion, such as shame, make one feel hot ? 



