Modeling of blood data. Modeling of blood data using blood deuterium-to-proton enrichment curves constructed from the authors' published illustrations and the following equation, assuming a negligible PB neutrophil lifespan: $bloodenrichment(t)=a*[urine enrichmentcurve(t−b)]$ where a is a scaling factor for the differing urine and blood deuterium enrichments, b is the time interval (delay) between the 2 time-enrichment curves, and t is time. The urine enrichment curve was constructed from the authors' simple exponential model. Fitting gave a delay of 11.2 days, similar to the sum (11.1 days) of the authors' mean values for marrow transit time and PB lifespan.