So the flat curve tells us that even if the partial pressure in the Alveoloi drops, hemoglobin will still be pretty much saturated. Now, let's move on to point number two. Now, within our tissues, if our tissues aren't active, if we're not actively exercising, then our partial pressure of oxygen inside the tissues, on average, is about 40 mercury. So we're about somewhere right here. Now, if we check out the corresponding Y value, we'll see that the percent saturation of hemoglobin at that partial pressure drops. Now, what does that mean?