6o 



THE VITAL PROCESSES 



7. By what means is pressure from contracting muscles in different 

 parts of the body made to assist in the circulation ? 



8. Of what advantage is the elasticity of the arteries? 



9. How is blood forced from the capillaries back to the heart? 



10. Why should there be a difference in structure between the two 

 sides of the heart ? 



11. Following Fig. 23, trace the blood through a complete circula- 

 tion, naming all the divisions of the system in the order of the flow of 

 the blood. 



12. If the period of rest following the period of contraction of the 

 heart be as long as the period of contraction, how many hours is the 

 heart able to rest out of every twenty-four? 



13. State the functions of the capillaries. Show how their structure 

 adapts them to their work. 



14. What kind of physical exercise tends to strengthen the heart? 

 What forms of exercise tend to injure it? State the effects of alcohol 

 and tobacco on the heart. 



15. How may rheumatism injure the heart? 



1 6. Give directions for checking the flow of blood from small and 

 from large blood vessels. 



PRACTICAL WORK 



In showing the relations of the different parts of the heart, a large 

 dissectible model is of great service (Fig. 24). Indeed, where the time 

 of the class is limited, the practical work may be confined to the study 

 of the heart model, diagrams of the heart and the circulation, and a few 

 simple experiments. However, where the course is more extended, the 

 dissection of the heart of some animal as described below is strongly 

 advised. 



Observations on the Heart. Procure, by the assistance of a butcher, 

 the heart of a sheep, calf, or hog. To insure the specimen against 

 mutilation, the lungs and the diaphragm must be left attached to the 

 heart. In studying the different parts, good results will be obtained by 

 observing the following order : 



1. Observe the connection of the heart to the lungs, diaphragm, 

 and large blood vessels. Inflate the lungs and observe the position of 

 the heart with reference to them. 



2. Examine the sac surrounding the heart, called the pericardium. 

 Pierce its lower portion and collect the pericardial fluid. Increase the 



