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264 EXPERIMENTAL PHYSIOLOGY. 



(CN) 6 in a 3% CuSO 4 solution. (3) Place a lump of fused CaCl 2 

 in a jar filled with saturated Na 2 CO 3 . Follow appearance daily 

 if possible. (4) Shake CHC1 3 with egg albumen. Examine under 

 microscope. The result is a collection of artificial cells each sur- 

 rounded by a film of protein. 



D. Osmosis. Prepare collodion bags in the following manner. 

 Pour 5 c.c. of the dissolved collodion into an absolutely clean 

 short test tube. Invert the test tube over the bottle of collodion, 

 allowing as much of the collodion to run back into the bottle as 

 will do so. Now rotate the test tube in the air, still inverted, until 

 the collodion is no longer liquid. Withdraw the ether vapour from 

 the tube by suction. Finally introduce some water into the test 

 tube, loosen the collodion membrane from the sides of the tube 

 and transfer the collodion bag to water. Fill one bag with molasses 

 and tie to a long glass tube. Suspend in H 2 O and mark the height 

 to which the liquid rises. Note rate of rise. Do the same with egg 

 albumen, 2 M sugar solution and 2 M NaCl. Recall in this con- 

 nection experiments already performed on Spirogyra, etc. How 

 do you account for the difference in behaviour of sugar and salt 

 solution of the same molecular concentration? Calculate from the 

 "gas laws" the height to which a 2 M solution of cane sugar should 

 rise if the colloidal bag w^ere absolutely impermeable to sugar, and 

 freely permeable to water. 



E. Surface tension. (1) Float a needle on the surface of H 2 O. 

 (2) Repeat with a soap solution. (3) What is the form of drops of 

 H 2 O falling from a pipette? Why? (4) Make a loop of wire and 

 attach to this a smaller loop of fine silk. Form a film on the wire 

 frame with soap solution. Wet a needle with soap solution and 

 pass through the film. Is the film ruptured? May this have any 

 relation to the passing of leucocytes through walls of capillaries? 

 Puncture the film within the silk loop. Result? Explain. 

 (5) Plateau's expt. 10 cc.. 60% alcohol in test tube. Add a drop of 

 olive oil (which should sink; if it does not, add 70% alcohol). Add 

 a small amount of 50% alcohol without stirring, then a drop of 

 olive oil (which should not sink; if it does, add more 50% alcohol.) 

 Find the mixture in which olive oil drops will sink part way but 

 not entirely to bottom. What is the form of the drops? Try to 

 change that shape with a glass rod. Result? Is there any differ- 



