Total Body Water (60% of body wt) - determined with deuterium oxide (heavy water), aminopyrine

Intracellular fluid (2/3's of body water; 40% of body wt)
Extracellular fluid (1/3 of body water; 20% of body wt) - determined by the inulin (from artichokes) volume. It consists of:
- Interstitial fluid (75%, 15% body wt)
- Blood volume (25%; 8% of body wt)
  - formed elements - Cr 51 tag to RBC's.
  - plasma (5% of body wt) - determined with Evans blue dye (T - 1824).