THE SENSES 413 



muscular walls. From the right ventricle, the blood is 

 driven out through the arteries, capillaries, and veins of 

 the lungs, where carbon dioxide is given off and oxygen 

 absorbed by the red corpuscles. 



Returning from the lungs, the blood enters the left auricle 

 and when this becomes full, passes through a valve into 

 the left ventricle. This has such powerfully muscular walls 

 that it is able to force the blood through- 

 out the body and back again to the 

 right auricle. As the blood leaves either 

 ventricle, there are valves that close and 

 prevent its return. If the hand is placed 

 a little to the left of the breastbone, the 

 strong contraction of the ventricle can 

 be felt. 



CROSS SECTION OF 

 THE HUMAN HEART 



The Senses. In order that the brain Showing aliricle ven . 

 may communicate with the outside world tricle, and ventricle 

 and so be able to protect the animal 

 from destruction and to provide for its well-being, animals 

 are provided with a number of sense organs which com- 

 municate with the brain by the nerves. The most con- 

 spicuous sensations of the human body are taste, smell, 

 touch, sight, and hearing. 



On the tongue and in the nose are cells which transmit to 

 the brain the impressions produced upon them by different 

 qualities, the one of solutions and the other of gases. The 

 sensations thus produced are called taste and smell. 



The sensation of touch originates in the skin and is much 

 more acute in some portions than in others. The tips of 

 the fingers in the blind are often trained to such delicate 

 perception that they, in a great degree, take the place of 



