Concepts of the body and of disease used in TCM are pseudoscientific, similar to Mediterranean humoral theory. TCM's model of the body is characterized as full of pseudoscience. Some practitioners no longer consider yin and yang and the idea of an energy flow to apply. Scientific investigation has not found any histological or physiological evidence for traditional Chinese concepts such as "qi", meridians, and acupuncture points. It is a generally held belief within the acupuncture community that acupuncture points and meridians structures are special conduits for electrical signals but no research has established any consistent anatomical structure or function for either acupuncture points or meridians. The scientific evidence for the anatomical existence of either meridians or acupuncture points is not compelling. Stephen Barrett of Quackwatch writes that, "TCM theory and practice are not based upon the body of knowledge related to health, disease, and health care that has been widely accepted by the scientific community. TCM practitioners disagree among themselves about how to diagnose patients and which treatments should go with which diagnoses. Even if they could agree, the TCM theories are so nebulous that no amount of scientific study will enable TCM to offer rational care."