PART Ⅰ．INTRODUCTORY

1．INTRODUCTION TO THE PROBLEM

2．＂ULTRAVIOLET LIGHT＂：A PROBLEM IN DEFINITION

Mode of Action of Light

What is Meant by＂Ultraviolet Light＂？

3．ABSORPTION OF ULTRAVIOLET LIGHT

Absorption and Penetration in Living Systems

Action Spectra and Absorption Spectra

Sources of Ultraviolet Light

Photochemical Consequences of Absorption

PART Ⅱ．SOME EFFECTS OF ULTRAVIOLET LIGHT ON BIOLOGICAL SYSTEMS

4．INACTIVATION AND LETHAL ACTION

Inactivation of Enzymes

Inactivation of Viruses

Lethal Effects on Microorganisms

Relation to Other Effects

5．HEMOLYSIS：CYTOLYSIS：LYSOGENY

Hemolysis

Cytolysis and Permeability Changes in Complex Cells

Lysogeny in Bacteria

6．COMPARISON WITH EFFECTS OF OTHER TYPES OF RADIATION

Photosensitized Oxidation(Photodynamic Action

Effects of Ionizing Radiations

O2-Dependence in Effects of Ultraviolet Light

In Summary

7．RECOVERY PROCESSES

Photorecovery

The Mechanism of Photorecovery

＂Catalase＂Restoration

In Summary

8．REPLICATION AND CELL DIVISION

Normal Cell Division

The Energetics and Kinetics of Cell Growth and Replication of Parts

The Mitotic Cycle

Replication of DNA，RNA，and Protein Molecules

Ultraviolet Light and the Timing of Cell Division

Delay of Cleavage in the Sea Urchin Egg

Locus of Action

Photorecovery

The＂Refractory＂Period

Relationship with Some Other Effects

Increase in Growth Rate in Cultures of Microorganisms

In Summary

9．INHERITED CHANGES

Mutation Within the Nucleus

Gene Mutation

Chromosome Aberrations

Polyploidy

Crossing-Over

Somatic Mutation

Inheritance and Inherited Changes in Microorganisms

Mutations

Cytoplasmic Inheritance and Nucleocytoplasmic Relationships

Killer Strains in Paramecium

Bacterial Transformations

Adaptation

Differentiation

Inheritance of the Tendency to Develop Cancer

The Cancer Cell

10．DEVELOPMENTAL GROWTH

Some Studies of Regeneration

11．ACUTE EFFECTS ON SKIN

Penetration of Ultraviolet Light

Sunburn of Human Skin

Erythema

Suntan

Immunity to Sunburn

Sunburn as an Inflammatory Response

Hyperplasia

Effects on Mouse Skin

Effect of Visible Light

In Summary

PART Ⅲ．EXPERIMENTAL CARCINOGENESIS WITH ULTRAVIOLET LIGHT

12．THE EXPERIMENTS

Quantitative Measurements of Tumor Development

Dosage and Development Time

Dose-Rate Dependence

Wavelength Dependence

Effect of Temperature

Tumor Types

Photorecovery

13．CELL PROLIFERATION AND THE GROWTH OF TUMOR MASSES

14．QUANTITATIVE INTERPRETATION OF THE EXPERIMENTS

Some Ideas That Do Not Fit

Are There Separable Periods of Induction and Growth？

Hypotheses Involving Somatic Mutation

Constant Acceleration of Growth Rate

An Approximate Model

The Completed Model

In Summary

15．SOME JUSTIFICATIONS AND AN EXTRAPOLATION

The Growth Curve

Clone Populations

Minor Effects

An Extrapolation

In Summary

16．SOME SPECULATION ABOUT THE MECHANISM OF CARCINOGENESIS

The Tem：A Hypothetical Particle

Are the Tems Virus Particles？

Is the Tem a Mutated Gene？

Control of Tumor Growth

The Question of Separable Stages in Cancerization

Are Immediate Chemical Carcinogens Formed by Ultraviolet Light？

Is the Tem a Common Denominator in Cancer？

In Summary

PART Ⅳ．SOME PRACTICAL CONSIDERATIONS

17．SUNLIGHT AND CANCER OF THE SKIN OF MAN

Skin Color and Cancer of the Skin

Topographical Distribution of Skin Cancer in Man

Distribution of Skin Cancer with Latitude

Relative Incidence in Indoor and Outdoor Workers

Other Diseases Caused by Light

In Summary

Prophylactic Considerations

18．SOME PROBLEMS OF EVALUATION

Accumulation of Effect of Environmental Carcinogens

Cancer in the Individual

Evaluation of Carcinogenic and Therapeutic Agents

PART Ⅴ．ENVOI

REFERENCES

INDEX