PRACTICAL WORK


*To demonstrate the Physical Properties of Blood* (Optional).—Since blood
is needed in considerable quantity in the following experiments, 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:

*1* Fill two thirds full. While the blood is cooling, stir rapidly with
the hand or a bunch of switches to remove the clot.

*2* Fill two thirds full and set aside without shaking or stirring.

*3* 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.*—1. Let some of the defibrinated blood (bottle 1) 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