Carbon dioxide diffuses in the opposite direction since the partial pressure is greater in the blood entering the lungs than it is in the alveolar air.
When the Baron looked down to see what was wrong, he saw a badger running in the opposite direction and his horse running off the trail, straight into the mire.
As you can see from the image below, oxygen moves out of the alveolus into the capillary, while carbon dioxide moves in the opposite direction - hence, the term gas exchange.
The idea being, if an earthquake causes the building to shift from left to right, the rod stretch and pull it back in the opposite direction, preventing the building from shaking itself to smithereens.