An organ causes chronic disease to repair the imbalance between the organ and the background organs. Although this process appears to be quite the same as that at acute disease, it is quite different in mechanism from that at acute disease. When background organs of organ-A, for instance, change their momenta simultaneously, they cause the imbalance in momentum with organ-A. In addition, an organ (organ-A) has very-small volume compared with the background organs. Thus, the imbalance in momentum works as a force, which starts oppressing organ-A. As a result, disease occurs in organ-A. In short, the difference in mechanism between acute and chronic disease makes us to take a mistake of treating disease; as a result, the disease tends to change itself into chronic one.

Interestingly enough, in this case, although background organs of organ-A firstly change their momenta, organ-A appears not only to change the momentum for itself but also to cause the disease for itself. Why? When background organs of organ-A change their momenta simultaneously, organ-A relatively changes the momentum compared with the background organs. Furthermore, organ-A has small volume compared with the background organs. Thus, even when background organs of organ-A firstly change their momenta simultaneously, organ-A appears to change the momentum for itself although it only relatively changes the momentum.

Next, by using simple models, explain this mechanism. As shown in the figures below, when background organs of organ-A raise, for instance, their momenta, organ-A will relatively reduce the momentum. In addition, organ-A has small volume compared with the background organs. Thus, nevertheless organ-A does not change the momentum, it appears to reduce the momentum for itself, and in addition to cause the imbalance in momentum with the background organs for itself. Then, to neutralize the imbalance in momentum, organ-A causes disease. Needless to say, although the fundamental cause of this type of disease originates in background organs of organ-A, it appears to originate only in organ-A. For the reasons, the majority of medical doctors think that its fundamental cause originates in organ-A, and try to treat the disease only by paying attention to organ-A. As a result, they will often fail to treat this disease and change the disease into chronic one by his mistake.