APPENDIX 183 



10. Ringer's solution (for frog tissues) 



Distilled water 1000.00 c.c. 



Sodium chloride (NaCl) 6.50 gm. 



Potassium chloride (KCl) 0.14 gm. 



Calcium chloride (CaCU) 0.12 gm. 



Sodium bicarbonate (NaHCOa) 0.20 gm. 



11. Salt solution (isotonic for frog tissues) 



Distilled water 1000.0 c.c. 



Sodium chloride (NaCl) 7.0 gm. 



12. Salt solution (isotonic for mammalian tissues) 



Distilled water 1000.0 c.c. 



Sodium chloride (NaCl) 9.0 gm. 



13. Starch paste (Exercise 9, Frog) 



Mix 10 c.c. of corn starch with 50 c.c. cold water. 

 Pour into 750 c.c. boiling water and boil two minutes. 



II. SUPPLEMENTARY DIRECTIONS FOR PHYSIOLOGICAL 



EXPERIMENTS 



A. Gastric Digestion (Exercise 8, Frog) 



Equipment for students: 



4 test-tubes for each pair of students. 



5 gummed labels for each pair of students. 



1 glass jar with cotton for each pair of students. 

 Equipment for general use: 



Several pipettes for transferring solutions. 



Test-tube brushes. 



Wash-bottles containing distilled water. 



Fibrin : soak in water and then cut into very small pieces. 



Hydrochloric acid (concentrated). 



Pepsin solution: A very concentrated solution in tap water. 

 This solution will not keep. 

 Directions for students: 



Students may work in pairs, but each must make the observa- 

 tions independently and write up the work. 



Clean the test-tubes with distilled water. 



Label each tube, telling what it is to contain, as directed in the 

 manual. 



