68 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



colloidal (greenish yellow or reddish) precipitate. With smaller amounts 

 of sugar the ppt. will appear on cooling. (Do not hasten cooling by 

 immersion in cold water). Cf. Bayliss, p. 126. 



8. Permeability of Protozoa. — Stain Paramecium in pond water plus 

 a trace of neutral red. Place a drop crowded with red Paramecia in 

 N/500 NaOH, another in N/500 NH4OH. Record time for color change 

 and for death in each case. Explain. Where does NaOH produce its 

 effect? Keep microscope free from solutions. Text pp. 246, 252. 



9. Do Ions or Molecules Penetrate? — Stain Spirogjrra in neutral red; 

 place in NaOH N/40; Ba(0H)2 N/40; and NH4OH N/40; watch under 

 microscope and record time for colour change in each case. As soon as 

 change is noted in filament, return it to pond water. Does red return? 

 Place cells stained with neutral red in NH4OH until yellow; then remove 

 to NaOH. Do they become red? Explain. Test permeability of cells 

 killed by saturated chloroform water. Cf. Mitchell, 1932, p. 453. Text 

 p. 251. 



10. Plasmolysis of Spirogyra. — Use only large healthy filaments 

 (preferably S. nitida). Compare cells in pond water and in 2M sugar. 

 Note osmotic distortion in this concentrated solution. 



Now place normal Spirogyra cells in M/2 M/3 



Cane sugar Cane sugar 

 Urea Urea 



Alcohol Alcohol 



Do they plasmolyse in each case? Note with care if plasmolysis is perma- 

 nent. Explain differences. Which substances penetrate most readily? 

 Which solutions have the same osmotic pressure? Observe ppt. of tannin 

 by urea. Young cells are more permeable according to Weber (cf. Hober, 

 Ann. Rev. Biochem., 1 : 14, 1932). Recovery from plasmolysis is a useful 

 test of penetration (cf. Stiles, "Permeability," p. 173, 1924). Text pp. 10, 

 247. 



11. Penetration of O2. — Carefully remove sartorius muscles from frog. 

 Stain each in .1% methylene blue in Ringer. Place on slides in Ringer. 

 Cover each with firmly oppressed cover-slip (no air bubbles). Note 

 color at edge. Gently steam one slide to kill muscle. Lift cover-slips 

 and observe time for return of blue color in each. Is dead muscle more 

 permeable to O2? Cf. Harvey, J. Gen. Phys., 5: 215, 1922. Text p. 258. 



12. Permeability of Erythrocytes. — Place a drop of frog's blood 

 corpuscles in distilled water in a watch-glass and examine quickly under 

 microscope. Place a drop of corpuscles in strong NaCl solution. Observe 

 effects (laking and crenation). Try .3M urea solution; it causes haemoly- 

 sis as if it were water. Dissolve the urea in .15M NaCl; effect? Explain. 

 Consult Ponder's monograph "The Mammalian Red Cell," 1934. Please 

 make sure that no solutions have touched microscope lens or stage. Text 

 p. 12. 



