Now, in the same time that the space inside the chest cavity increases, what also increases is the space inside the intraplural space. So the volume inside this entire region that is found between the parietal and the visceral plural, basically increases. Now, let's recall Boils Law. We know that in physics, boyle's Law describes the relationship between volume and pressure when the temperature is held constant. And because our body is at a constant temperature of 36.7 degrees Celsius, we can assume that this obeys Boil Law, meaning the temperature is constant. Now, Boyle's Law tells us that the pressure multiplied by the volume is equal to a constant value.