THE CELL; THE COLLOIDAL CONDITION 19 



QUESTIONS 



1. Why are plant cells with walls and animal cells generally without? 

 2 What are the advantages of a cellular structure? 



3. Are any cells of a plant useful when dead? 



4. Should Hooke really be given credit for discovering the cell? Why? 



5. Why had cells not been discovered by the Greeks? 



6. Why are emulsions, suspensions, and gels most important of all the 

 colloidal mixtures for a physiologist? 



7. Among these mixtures, why is a gas within a gas not mentioned? 



8. A plant is 40-95% water. Why is it able to retain its shape and form? 



9. An Elodea leaf is about 1 cm. long and 2 mm. wide. If the leaf is 100 cells 

 long and 50 cells wide, and if each cell is square in cross section, what is the 

 total cell surface exposed by one layer of cells? 



10. What are the laws of thermodynamics? 



11. Define electrolyte, caseinogen, and surface tension. 



12. Discuss the construction and use of the ultramicroscope. 



13. What is the "Tyndall effect"? 



14. What is Brownian movement? 



15. Who was Francesco Selmi and what was the relation of his work to that 

 of Graham? 



REFERENCES 



Bradford, S. C. — Colloids or the materials of life. Sci. Prog., 17:120, 1922. 

 Foster, N. — Colloids and living phenomena. Set. Mo., 9:465, 1919. 

 Gerould, G. H— The dawn of the cell theory. Sci. Mo., 14:268, 1922. 

 Grey, E. C— The importance of surface for life. Cairo Sci. Jour., 12:67, 1924. 

 Harper, R. A.— The structure of protoplasm. Am. Jour. Bot., 6:273, 1919. 

 Heilbrunn, L. — The colloid chemistry of protoplasm. Am. Jour. Physiol., 



64:481, 1923. 

 Lepeschkin, W. W. — My opinion about protoplasm. Protoplasma, 9:269, 



1930. 

 MacDougal, D. T., and Spoehr, H. A.— Components and colloidal be- 

 havior of plant protoplasm. Proc. Am. Phil. Soc, 59:150, 1920. 

 Morgan, J. R.— Robert Hooke (1635-1703). Sci. Prog., 25:282, 1930. 

 Murray, H— A short review of colloidal theory. Sci. Prog., 15:234, 1920. 

 Priestley, J. — Colloids and proteins in plant physiology. Sci. Prog., 16:201, 



1921. 

 Rich, A. R— Place of R. J. H. Dutrochet in the development of the cell 



theory. Bui. Johns Hopkins Hospital, No. 39:330, 1926. 

 Seifriz, W— The structure of protoplasm by aid of micro-dissection. Biol. 



Bui, 34:307, 1918. 

 Wilson, E. B., Chambers, R., Seifriz, W., Mast, S. O., and Heilbrunn, 



L. V. — Symposium on the structure of protoplasm. Am. Nat, 60:105, 



1926. 



