Next, let us consider how a tissue causes chronic inflammation. Because atrophic change is one of the representative pathological changes seen in chronic inflammation, begin by considering theoretically how a tissue causes atrophic change. Then, by using the conclusion, let us find out the special characteristics of chronic inflammation.

(a) Outbreak Mechanism of Atrophic Change
A tissue with chronic inflammation tends to decrease its own volume; this phenomenon can be considered to occur by the opposite mechanism to swelling change. Specifically, a tissue can theoretically be considered to cause atrophic change through two steps. At the first step, a tissue with chronic inflammation reduces the momentum relatively to the background tissues, and loses the balance in energy density with the background tissues. At the next step, to neutralize the imbalance in energy density, the tissue increases the energy density by decreasing the volume. As a result, the tissue becomes atrophied. (Notice that when a system decreasing the momentum reduces the energy density, it decreases the volume to raise the energy density.)

The important point is to notice the fact that the fundamental cause of chronic inflammation usually originates in the background field of an organ. Always when a tissue shows strong change, it appears to cause it for itself. However, a tissue often causes inflammation due to the background field; this type of inflammation frequently occurs as chronic inflammation. Specifically, when the background field of a tissue changes the momentum, it causes the imbalance in momentum with the tissue. Then, in order to neutralize the imbalance, the tissue causes inflammation. If medical doctors can notice this mechanism, they will be able to treat this inflammation completely and stop changing it into chronic one.