Extra nitrogen dissolves into the blood of divers who breathe compressed air while diving deep underwater. If the divers return to the surface too quickly, the dissolved nitrogen bubbles out of their blood. These bubbles block blood flow to muscles, organs, and the brain, often leading to death. For many years, scientists could not understand why other mammals such as seals could make extended dives into deep water and not develop this condition called “the bends.”
They found the answer by using a backpack to monitor the seal's heart rate, sample its blood, and record its diving depth. True to the laws of physics, nitrogen accumulated in the seal's blood as it descended deep into the ocean. However, the nitrogen concentration leveled off in the seal's blood just before reaching a dangerous point. Scientists discovered that the tiny sacks in the seal's lungs which absorb air in order to pass oxygen into the blood stream, simply shut down once the nitrogen level in the blood gets too high. At the same time, the seal's heart, liver, and blubber begin to absorb the nitrogen from the blood. As the seal ascends to the surface, the air exchange sacks in the lungs reactivate. A complex system like this could only be the result of design.
From A Closer Look at the Evidence by Kleiss, February 19.
