CHAP, x CIRCULATION OF THE BLOOD 121 



ing from every cell the substances which would cause 

 disease and death. 



94. The Heart. In studying absorption we learned 

 that the foods taken into the blood from the alimentary 

 canal both by the direct and the indirect methods are 

 brought together in the right side of the heart. 



The heart is about the size of a person's clenched fist 

 In an adult it is about five inches long and three and 



FIG. 61. The lungs, heart, and large blood vessels, front view (Zuppke). 



one half inches thick, and weighs about ten ounces. It 

 is situated at the center of the chest between the lungs, 

 with its apex inclined to the left and front. For this 

 reason you can feel the heart beat best if you place 

 your hand over the left side of the chest on a level 

 with the lower part of the breastbone. The heart has 

 a saclike covering, resembling the pleura of the lungs, 

 folded around it ; this is the pericardium. There is a 

 small amount of fluid in this sac, which serves to oil 



