PART Ⅰ．INTRODUCTORY 1
1．INTRODUCTION TO THE PROBLEM 3
2．＂ULTRAVIOLET LIGHT＂：A PROBLEM IN DEFINITION 9
Mode of Action of Light 9
What is Meant by＂Ultraviolet Light＂？ 11
3．ABSORPTION OF ULTRAVIOLET LIGHT 17
Absorption and Penetration in Living Systems 17
Action Spectra and Absorption Spectra 23
Sources of Ultraviolet Light 30
Photochemical Consequences of Absorption 34
PART Ⅱ．SOME EFFECTS OF ULTRAVIOLET LIGHT ON BIOLOGICAL SYSTEMS 37
4．INACTIVATION AND LETHAL ACTION 39
Inactivation of Enzymes 39
Inactivation of Viruses 44
Lethal Effects on Microorganisms 48
Relation to Other Effects 51
5．HEMOLYSIS：CYTOLYSIS：LYSOGENY 52
Hemolysis 52
Cytolysis and Permeability Changes in Complex Cells 57
Lysogeny in Bacteria 60
6．COMPARISON WITH EFFECTS OF OTHER TYPES OF RADIATION 62
Photosensitized Oxidation(Photodynamic Action 63
Effects of Ionizing Radiations 68
O2-Dependence in Effects of Ultraviolet Light 70
In Summary 73
7．RECOVERY PROCESSES 75
Photorecovery 75
The Mechanism of Photorecovery 79
＂Catalase＂Restoration 85
In Summary 86
8．REPLICATION AND CELL DIVISION 88
Normal Cell Division 89
The Energetics and Kinetics of Cell Growth and Replication of Parts 90
The Mitotic Cycle 96
Replication of DNA，RNA，and Protein Molecules 100
Ultraviolet Light and the Timing of Cell Division 103
Delay of Cleavage in the Sea Urchin Egg 104
Locus of Action 106
Photorecovery 109
The＂Refractory＂Period 109
Relationship with Some Other Effects 113
Increase in Growth Rate in Cultures of Microorganisms 116
In Summary 117
9．INHERITED CHANGES 119
Mutation Within the Nucleus 121
Gene Mutation 122
Chromosome Aberrations 123
Polyploidy 124
Crossing-Over 124
Somatic Mutation 124
Inheritance and Inherited Changes in Microorganisms 125
Mutations 126
Cytoplasmic Inheritance and Nucleocytoplasmic Relationships 127
Killer Strains in Paramecium 127
Bacterial Transformations 127
Adaptation 128
Differentiation 130
Inheritance of the Tendency to Develop Cancer 134
The Cancer Cell 135
10．DEVELOPMENTAL GROWTH 138
Some Studies of Regeneration 143
11．ACUTE EFFECTS ON SKIN 155
Penetration of Ultraviolet Light 156
Sunburn of Human Skin 160
Erythema 161
Suntan 165
Immunity to Sunburn 166
Sunburn as an Inflammatory Response 169
Hyperplasia 169
Effects on Mouse Skin 170
Effect of Visible Light 179
In Summary 180
PART Ⅲ．EXPERIMENTAL CARCINOGENESIS WITH ULTRAVIOLET LIGHT 183
12．THE EXPERIMENTS 185
Quantitative Measurements of Tumor Development 186
Dosage and Development Time 188
Dose-Rate Dependence 194
Wavelength Dependence 196
Effect of Temperature 199
Tumor Types 199
Photorecovery 203
13．CELL PROLIFERATION AND THE GROWTH OF TUMOR MASSES 205
14．QUANTITATIVE INTERPRETATION OF THE EXPERIMENTS 216
Some Ideas That Do Not Fit 216
Are There Separable Periods of Induction and Growth？ 216
Hypotheses Involving Somatic Mutation 220
Constant Acceleration of Growth Rate 223
An Approximate Model 225
The Completed Model 230
In Summary 242
15．SOME JUSTIFICATIONS AND AN EXTRAPOLATION 243
The Growth Curve 243
Clone Populations 251
Minor Effects 253
An Extrapolation 255
In Summary 258
16．SOME SPECULATION ABOUT THE MECHANISM OF CARCINOGENESIS 260
The Tem：A Hypothetical Particle 260
Are the Tems Virus Particles？ 268
Is the Tem a Mutated Gene？ 270
Control of Tumor Growth 271
The Question of Separable Stages in Cancerization 272
Are Immediate Chemical Carcinogens Formed by Ultraviolet Light？ 274
Is the Tem a Common Denominator in Cancer？ 276
In Summary 280
PART Ⅳ．SOME PRACTICAL CONSIDERATIONS 283
17．SUNLIGHT AND CANCER OF THE SKIN OF MAN 285
Skin Color and Cancer of the Skin 288
Topographical Distribution of Skin Cancer in Man 292
Distribution of Skin Cancer with Latitude 295
Relative Incidence in Indoor and Outdoor Workers 302
Other Diseases Caused by Light 303
In Summary 303
Prophylactic Considerations 304
18．SOME PROBLEMS OF EVALUATION 306
Accumulation of Effect of Environmental Carcinogens 306
Cancer in the Individual 309
Evaluation of Carcinogenic and Therapeutic Agents 310
PART Ⅴ．ENVOI 321
REFERENCES 323
INDEX 337