ANATOMY, PHYSIOLOGY, &C. 255 



simultaneous in all parts of the body, the feeling of 

 one pulse is therefore equal to the feeling of more 

 than one, for they suppose that local disease may 

 make a difference. 



Involuntary Motion. 



The organs of involuntary motion are those of 

 digestion, circulation, and respiration. These go on 

 continually, not being subject to intermission from 

 exhaustion, as the voluntary are, which require re- 

 pose and sleep to recruit themselves. 



Vibrations. 



Hartley explains the successive trains of thoughts, 

 or association of ideas, by vibrations and vibratiun- 

 cles of the nerves, parts that do not vibrate, and 

 which, if placed in any situation where they could be 

 made to vibrate, would be no longer capable of trans- 

 mitting sensation. 



The Heart. 



The essential difference as to the general struc- 

 ture of the heart, between amphibious and mere land 

 animals, or such as never go into the water, is, that 

 in the first the foramen ovale remains always open. 

 Through this there is a communication, and the cir- 

 culation is kept up, although the animal does not 

 respire under the water. 



The heart may be regarded merely as an enlarge- 

 ment of the veins. 



The ventricle propels the blood through the pul- 

 monic arteries, by which pulsation is occasioned. 



Those vessels are termed arteries into which the 

 ventricles of the heart discharge themselves. 



The Eye. 

 - There are two coats which may be considered as 



