402 FOODS CIRCULATED AND USED IN THE BODY 



Laboratory Exercise. What methods should be used to stop the 

 flow of blood in case of an accident ? Decide first whether the blood is 

 issuing from an artery or from a vein. How would you know? Then 

 apply a tourniquet made from a stick or ruler and a handkerchief or 

 towel, using a stone or knife to press down on the blood vessel. 



Imagine an artery severed in the arm below the elbow and practice 

 applying a tourniquet there. Apply a tourniquet, if the artery cut is 

 above elbow. Does the pulse in the wrist stop when the tourniquet is 

 applied ? Explain reason. 



Conclusion. How would j r ou make a tourniquet? Describe fully. 

 Where must a tourniquet be placed when an arteiy is cut? Where 

 when a vein is severed ? What is the use of the tourniquet ? 



The effect of alcohol upon the blood. Alcohol, when taken 

 habitually, causes several very serious effects upon the blood and 

 blood vessels. The bodily resistance against disease which is 

 brought about by the presence of specific antibodies is greatly 

 weakened in those who use alcohol to excess. Drinking also has 

 an injurious effect upon the colorless corpuscles, as it lowers their 

 ability to fight disease germs. Place a drop of alcohol on a slide 

 containing active amoebas, if 3 r ou wish to see the effect on a similar 

 type of cell Alcohol acts on the nerve centers controlling the 

 heart and blood vessels. Alcohol may even, in cases of long and 

 severe drinking, cause changes to take place in the walls of the 

 blood vessels which may result in the breaking of the vessel or the 

 formation of a blood clot in the vessel. Such an injury in blood 

 vessels in the brain causes apoplexy and often results in sudden 

 death. 



Self-Testing Exercise 



The circulation of the blood is brought about by a heart which acts 



as a ........ (1) (2). Blood passes out from the heart 



through (3), then into the tissues by means of the (4), 



returning to the heart again by way of the (5). There are 



two important systems of circulation in the body : the (6) to 



and from the lungs, and the (7) which leaves the heart from 



the (8) ventricle and passes out to all the body organs. 



Arteries are (9) and (10), capillaries are very 



(11), and veins have (12) walls and have 



(13) to keep the blood from running backward. The pulse is caused 

 by the gushing of blood from the (14), when the walls of the 



