Shows how various viruses fit between the largest non-living molecule and the smallest unit of life. Uses models to explain the organization of various kinds of molecules and viruses. Reviews the first experiment in which a virus was isolated, purified, and crystallized. Concludes with a discussion on the importance of viruses in the understanding of all living matter.

Presents an analysis of the structure of viruses and how they are studied. Shows and explains how an electron microscope works. Uses film clips of experiments to demonstrate the cultivation, isolation, and purification of viruses. Concludes with a discussion of the differences between viruses.

Dr. C. Arthur Knight, featured on this program, introduces his topic with a brief description of properties which characterize living things, and then explains to what degree viruses do or do not have these properties. What is significant, he points out, is that viruses are like other living things to the extent that they are capable of reproducing themselves. Because viruses have a chemical content, similar to that of chromosomes — the cells which determine heredity — and because they can be more easily isolated and fragmented than chromosomes, they are a source of much information for scientists who study life's creation and formation. In addition to his general points, Dr. Knight shows, through a remarkable series of micro-motion pictures, how mutations within viruses can be formed and identified.

Presents an analysis of bacteriophages and how they may change. Explains why bacterial viruses are useful to scientists studying different life forms. Uses diagrams and animation to show how bacteria reproduce within a cell and how mutations of these viruses can be identified. Describes the "copy errors" responsible for mutation, and the ways in which cross-breeding among viruses takes place.

Explains how a virus destroys cells. Uses animated films and microcinematography to show how a virus enters a cell, stops its normal functions, and reproduces more viruses. Tells how the new viruses are made and describes their method of escape to infect other cells. Concludes with a discussion of possible methods of controlling viral diseases.

Presents an analysis of nucleic acid. Uses a large model of the tobacco mosaic virus to explain its structure. Demonstrates how a virus can be reconstituted from nucleic acid and protein molecules. Discusses the recent discovery of the alteration of nucleic acid to form mutations of the original virus. Concludes with a theory which may account for the way in which genetic information is stored in nucleic acid and then translated into a specific protein structure.

Discuses virus diseases. Reviews the known viral diseases and the development of vaccination. Explains how a polio virus attacks a cell. Analyzes the activity of viruses, which cause cancer in animal cells. Demonstrates how virus cultures can be grown and used for inoculation. Concludes by discussing cures for viral diseases.