48 



EXPERIMENTAL PHYSIOLOGY 



vailing direction of flow of the water? Is the color of the 

 water in the outer jar changed? Has some of the salt solu- 

 tion in the dialyzer passed through the membrane? (This 

 interchange of water and salt solution through a non-porous 

 membrane — the sausage skin — is called osmosis.) 



B. Chop up some raisins and place in a beaker with some 

 water. When the grape sugar in the raisins is well dis- 

 solved, transfer this liquid to the dialyzer. Fill both dialyzer 

 and outer jar to the same level with water as before. Note 

 the direction of the water-flow. Test the water in the outer 

 jar with Fehling's solution. What results? Does grape 

 sugar in solution pass readily through the membrane? 

 (Substances which pass readily in solution through a mem- 

 brane under the above conditions may be said to dialyze.) 



(7. Substitute for the raisin solution a diluted starch paste. 

 After a time note the level of the water. Record its direc- 

 tion of flow. Test the liquid in the outer jar with iodine 

 solution. Does starch dialyze? Does starch crystallize like 

 grape sugar and potassium bichromate? 



D, Substitute for the 

 starch paste a solution 

 made of white of egg 

 whipped up in water. 

 Note direction of flow of 

 water. Test the water in 

 the outer jar with Millon's 

 test for proteid. Does 

 egg albumin dialyze? 



E, Cut a few slices 

 of beet root. Wash and 



place a few pieces in two separate beakers. Fill each 

 beaker half full of distilled water. Boil the sUces in one 



Fig. 23. — A, living cell; B, cell whose proto- 

 plasm has been killed by boiling; cw, cell 

 wall; n, nucleus; p, protoplasm. 



