1. INTRODUCTION
1.1. Basic Principles of Detecting Hot Gas
1.2. Early Developments
1.3. Current Topics
1.4. Outline of This Paper—A Summary
2. FUSE OBSERVATIONS, DATA REDUCTION, AND ANALYSIS
2.1. Sample Selection
2.2. FUSE Observations
2.3. Sub-Exposure Corrections and Co-Addition
2.4. Wavelength-scale Accuracy and Zero-Point Correction
2.5. The O VI Wavelength Region and Contaminating Lines
2.6. Continuum Fitting
2.7. Removal of the HD 6 − 0 R(0) Line
2.8. Measurement of O VI Absorption Lines
2.9. Misleading Effects from Unrecognized Saturation?
2.10. The Final FUSE Sample
3. INTERPRETATION
3.1. Inclusion of Other Data Sets
3.2. Distribution of Stars in the Galactic Plane
3.3. Variability of O VI Absorption Lines Determined from Multi-epoch Data
3.4. Accounting for Circumstellar Bubbles
3.5. Accounting for Supernova Remnants
3.6. ROSAT Categories For Other Datasets
3.7. Average O VI Line of Sight Volume Density
3.8. O VI Mid-Plane Volume Density
3.9. Distribution of O VI Column Density with Effective Distance
3.10. Variation of O VI volume density with Milky Way Spiral Arms
3.11. Variation of O VI Velocity with Galactic Longitude
3.12. Comparison of Low and High Ion Velocity Extremes
3.13. Minimum O VI Line Widths
3.14. Distribution of O VI Column Density with Doppler Parameter, and with Distance
4. SUMMARY