APPLIED PHYSIOLOGY 



4. Each ventricle contracts upon the blood about seventy- 



two times a minute, forcing it out through a tube 

 called an artery. 



5. Blood is kept from running back into the heart by a 



valve at the beginning of the artery. 



6. The heart contains a nervous mechanism which 



makes it partially independent of the rest of the 

 body. 



7. The heart has great power of resistance against 



disease, and of accommodating itself to increased 

 work, so that heart disease is less to be feared 

 than disease of almost any other part of the 

 body. 



8. Alcohol at first causes the heart to beat faster and 



more strongly than the body needs, thus causing 

 it to tire itself out. 



9. Alcohol soon weakens the heart by impairing its nutri- 



tion. 



10. Tobacco makes the heart beat irregularly and with 

 less power. 



DEMONSTRATIONS 



70. The left side of a chicken's heart closely resembles a man's 

 left auricle and ventricle, and can be used to show the cavities and 

 valves. In removing it, be careful to preserve its covering of peri- 

 cardium. A pig's, or sheep's, or bullock's heart is more like a human 

 heart. The butcher should be instructed not to cut off the auricles. 

 (See demonstration 35.) 



71. The heart of a frog or fish which has just been killed should be 

 removed to show its persistence in beating. (See demonstration 35.) 



72. Have the students listen to each other's hearts so as to get 

 a clear idea of the two sounds. Feel the heart beats upon the chest, 

 and notice how they increase in force and frequency when a person 

 rises after lying down, and more yet when he walks and runs. 



