Chap. XX] 



SUMMARY 



433 



SUMMARY 



' Perception through the sense organs. 



Sensation 



Organs 

 necessary 

 for sensa- 

 tion 



Classification < 



End organ for the reception of a stimulus. 

 A nerve for conduction of the stimulus. 

 A centre in the brain for the perception and 

 interpretation. 



1. Internal or those in 



which the sensa- 

 tions are pro- 

 jected to the in- 

 terior of the 

 body. 



2. External or those in 



which the sensa- 

 tions are pro- 

 jected to the ex- 

 terior of the 

 body. 



Hunger. 



Thirst. 



Pain. 



Muscular sense. 



Fatigue. 



Visceral sensations . 



Pressure. 



Temperature. 



Taste. 



Smell. 



Hearing. 



Sight. 



Hunger 



Thirst 



Pain 



Presumably due to contractions of empty stomach, act- 

 ing on nerves distributed to mucous membrane. 



In abnormal conditions it may be due to failure to assimi- 

 late food. 



/ Presumably due to stimulation of nerves of pharynx by 

 1 low water content in tissues. 



f May be due to stimulation of special nerve endings, or to 



I overstimulation of any of the sensory nerves. 

 Muscular Sense — Due to stimulation of sensory nerves distributed to 



muscles. Weight or resistance serves as stimulus. 

 Fatigue — Due to stimulation of sensory nerves distributed to muscles. 



Loss of nutrient material or accumulation of waste products 



acts as stimulus. 

 Visceral Sensations — Due to stimulation of sensory nei-ves distributed 

 to the \'iscera. 



r End organs distributed over entire surface of body. 

 Pressure • | -^ j / Nerve filaments surround hair foUicles. 



i 1 Tactile or Meissner corpuscles. 



End organs distributed over entire surface of body. 



r Temperature higher than body. 

 Hot spots I Carbon dioxide. 

 Temperature { ^^^ organs J Electricity. 



^ ( Temperature lower than body. 



Cold spots I Menthol. 

 I Electricity. 

 2f 



