The physiology of traditional Chinese medicine has many similarities to that of Western medicine. Most of the specific organ functions defined in the Nei Ching Su Wen are astonishingly accurate in the light of modern scientific discoveries. The heart is said to dominate the circulation of the blood. The Nei Ching Su Wen says, 'The heart fills the pulse with blood . . . and the force of the pulse flows into the arteries and the force of the arteries ascends into the lungs'. This seems to be a clear description of the circulation of the blood through the body, via the lungs. The idea that blood circulated in this way was peculiar to Chinese medicine until it was 'rediscovered' by William Harvey in the early seventeenth century. The publication of Harvey's work Du Mote Cordis has subsequently been hailed as one of the great landmarks of Western medicine, although at the time Harvey was thought to be mad, 'inflaming the medical profession by the suggestion of such a preposterous idea'. The Nei Ching Su Wen also makes some surprising observations about the kidneys. It states that the kidneys dominate bone, that they play an integral part in the process of growth and reproduction (in fact the Chinese character for kidney and testicle is sometimes indistinguishable) and that the kidneys control body fluid in concert with the lungs. During the last forty years it has become obvious that vitamin D is a very important factor in bone growth, and if it is not present then rickets results. The exact mechanism of this disease process was unclear as it was not really understood how vitamin D actually worked, but recently it has been shown that the kidney provides the missing link in the control of bone growth and development, by changing the chemistry of vitamin D. The idea that the 'kidney dominates bone' is therefore an accurate, detailed, complex and surprising observation to have been made some 2,500 years ago. Embryology is the study of the growth and development of the foetus in the mother's womb. With the advent of good microscopic technique, in the early part of this century, embryology developed apace. It has been shown, quite conclusively, that both the ovaries and the testicles develop from the same original cells as the kidney. This process begins when the foetus is about five weeks old, (when a baby is born it is said to be in its fortieth week of development). The kidneys therefore, do seem to play an important part in the process of growth and reproduction. The detailed and specific control of body fluid is a very complex chemical system, and one that we are only just beginning to understand properly, but it is quite obvious that the kidney and the lung do work together to control the fluid in our bodies. Most of this information has become available since the Second World War, with the development of complex and expensive machines to look at small changes in the chemicals and fluid within the body.