THE BLOOD 



37 





1 1 . What habits of living favor the development of corpuscles in 

 the blood ? 



12. Why will keeping the skin clean and active improve the quality 

 of one's blood ? ^x^ 



PRACTICAL WORK 



monstrate the Physical Properties of Blood (Optional) 



Since blood is needed in considerable quantity in the following experi- 

 ments, it is best obtained from the butcher. To be sure of securing the 

 blood in the manner desired, take to the butcher three good-sized 

 bottles bearing labels as follows : 



Fill two thirds full. 

 While the blood is 

 cooling, stir rapidly 

 with the hand or a 

 bunch of switches to 

 remove the clot. 



Fill two thirds full 

 and set aside without 

 shaking or stirring. 



Fill two thirds full 

 and thoroughly mix 

 with the liquid in the 

 bottle. 



Label 3 must be pasted on a bottle, having a tight-fitting stopper, 

 which is filled one fifth full of a saturated solution of Epsom salts. The 

 purpose of the salts is to prevent coagulation until the blood is diluted 

 with water as in the experiments which follow. 



Experiments. i. Let some of the defibrinated blood (bottle i) 

 flow (not fall) on the surface of water in a glass vessel. Does it remain 

 on the surface or sink to the bottom ? What does the experiment 

 show with reference to the relative weight of blood and water ? 



2. Fill a large test tube or a small bottle one fourth full of the defi- 

 brinated blood and thin it by adding an equal amount of water. Then 

 place the hand over the mouth and shake until the blood is thoroughly 

 mixed with the air. Compare with a portion of the blood not mixed 

 with the air, noting any difference in color. What substance in the air 

 has acted on the blood to change its color ? 



3. Fill three tumblers each two thirds full of water and set them in 

 a \s r arm place. Pour into one of the tumblers, and thoroughly mix with 

 the water, two tablespoonfuls of the blood containing the Epsom salts. 

 After an interval of half an hour add blood to the second tumbler in the. 



