Kidney (shen) and Portal of Life (mingmen), Chinese, Ming

Woodcut depicting the kidneys; illustration of 'Problem 36' from Tu zhu ba shi yi nan jing bianzhen (Corrected Edition of the Canon of Problems, Illustrated and Annotated), published in the Wan Li reign period of the Ming Dynasty (1573-1620). The image illustrates the distinct physiological functions of the left and right kidneys in Chinese medical theory. The left kidney, or kidney (shen) proper, partakes of the nature of water, while the right kidney, the mingmen (Portal of Life) partakes of the nature of fire. The mingmen is crucial to life; it is the place where innate Qi is stored, the origin of life processes, the very root of existence. The fire in mingmen is expressed in the Yang functions of the kidneys (in modern times, taken to include the function of the adrenal gland). There were two views of the mingmen in ancient Chinese medicine. According to one theory, it corresponded to the right kidney; according to the other, it corresponded to both kidneys, as embodied in the dynamic interchange of Qi between them. The first theory is represented in this diagram.

Fire and water work together; it is the habitation of all spirits and essences. It is the place where original Qi resides. In fire, the male stores essence (sperm). In water, the female has her womb. The two kidneys are not both kidneys (shen). The left one is the kidney, but the right one is the mingmen. Know therefore that there is only one kidney.