342 Constant Care Is Needed for Health unit \t 



3. What is a filterable virus? Give two reasons why little progress could 

 be made in virus study until recently. 



4. Why do some bacteriologists believe a virus to be alive; others, 

 lifeless? 



5. Name some common diseases caused by a virus. Against \\ hich four 

 virus diseases has a vaccine been developed? 



6. What is a bacteriophage? Where is it found? How useful has bac- 

 teriophage proved itself to be in conquering disease? 



7. What can you say about the future of bacteriology? 



Exercises 



1. This recent work is so technical that vou can do no experimentation 

 in connection with it. Instead, make sure that vou understand what vou 

 have read on advances in the germ theory of disease by summarizing the 

 facts in two columns headed "Startling Facts about Strains of the Same 

 Species of Bacterium," and "Startling Facts about Chemically Prepared 

 Substances Used as Antibodies and Vaccines." 



2. Sum up your understanding of a virus in a table under the following 

 headings: Characteristics of a Virus; Reasons for Believing a Virus Is 

 a Living Thing; Reasons for Believing That It Is Not Living; Diseases 

 Caused by a Virus; Virus Diseases against Which We Have Vaccines. 



Further Activities in Biology 



1. You will find rather difficult but interesting reading in Frederick 

 Eberson's The Microbe's Challenge, Jaques Cattell Press, 1941. Report 

 to the class on some topic such as viruses or bacteriophage. 



2. Look through the recent files of the Science News Letter for infor- 

 mation on viruses. 



