276 THE INCOME OF ENERGY 



Physical Changes in Coagulation. 1. Clotting 

 of Plasma. Wet a small filter with cane-sugar 

 solution (0.5 per cent). Cut a frog's ventricle 

 across near the base so that 0.5 c.c. blood shall fall 

 into a beaker containing an equal quantity of cane- 

 sugar solution. Pour the mixture on the filter. 

 Receive the filtrate on a watch-glass. Note the 

 physical changes in this filtrate. 



2. Fibrin Threads. Place a blood-drop under 

 a cover-glass. With the microscope observe the 

 appearance of fibrin threads. 



3. Receive 1 c.c. blood into 0.5 c.c. saturated 

 solution MgS0 4 . Note (1) absence of clotting, 

 and (2) its appearance after dilution. 



4. Receive 0.5 c.c. blood in a watch-glass. 

 Let it stand twenty-four hours. Note physical 

 changes during the first ten minutes and at 

 end of period. 



SECRETION 



Speed of Absorption and Secretion. Place 

 5 c.c. of thin starch paste and 2 c.c. concentrated 

 nitric acid in each of ten test-tubes and mark 

 them 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 

 minutes. Let one of each pair of students swal- 

 low a gelatine capsule containing ten grains of 

 potassium iodide. 1 Immediately rinse the sub- 



1 The subject should have had a small, early breakfast. 



