2 VITAMINS A AND CAROTENES 



2. Bone, Postnatal 116 



3. Bone Growth and the Nervous System 119 



C. Hypervitaminosis A 124 



1. Pathologic Physiology 124 



2. Skeletal Responses 125 



3. Teeth 133 



4. Epithelial Tissues and Organs 133 



D. Prenatal Consequences of Vitamin A Deficiency 135 



E. Summary 136 



VIII. Effects of Vitamin A Deficiency in Human Beings 137 



A. General Considerations 137 



1. "Primary" and "Secondary" Deficiency 137 



2. Deficiency in Human Volunteers 138 



3. Nutrition Surveys 139 



4. Clinicopathologic Studies 139 



5. Vitamin A and Epithelia 140 



B. Night Blindness 141 



1. Vitamin A in the Visual Purple Cycle 141 



2. Measurement of Night Blindness 142 



C. Xerophthalmia and Keratomalacia 142 



1. Early Investigations 143 



2. External Manifestations 144 



3. Histopathology 145 



4. Response to Therapy 147 



D. Metaplasia of Epithelia (Internal) 147 



1. Post-Mortem Material 148 



2. Epithelial Metaplasia 148 



E. Cutaneous Lesions 149 



1. Macroscopic Features in Adults 149 



2. Macroscopic Features in Infants and Children 154 



3. Histopathology 157 



F. Massive Vitamin A Therapy in Clinical Medicine 159 



G. Hypervitaminosis A 161 



IX. Requirements 163 



A. Of Animals 163 



1. General Considerations 163 



2. Rats and Mice 164 



3. Rabbits 166 



4. Dogs 166 



5. Foxes and Minks 166 



6. Horses 166 



7. Swine 167 



8. Cattle 167 



9. Sheep 167 



10. Chickens 169 



11. Turkeys 170 



12. Insects 170 



B. Of Human Beings 171 



1. The International Unit ' 171 



2. Requirements for Carotene 171 



