Part of the diagnostic techniques of acupuncture is the assessment of the tongue. This involves only a quick inspection, but encompasses details of the coating, colour, texture and symmetry of the body of the tongue. Similarly to iridology, this provides a window to the inner workings of the body.
This practice has been used for thousands of years within the Traditional Chinese Medicine and the Indian Ayurvedic systems, but was also routinely conducted by doctors in the UK, using western terminology, until recent generations.
The tongue has many relationships and connections in the body, both to the meridians, and the internal organs. It is therefore very useful and important during inspection for confirming diagnosis and, I find, as an excellent tool for self learning as it will present strong visual indicators of your overall health.
In 1987, a paper was published in the Chinese language ‘Journal of Oncology’, examining the tongues of more than 12,000 patients. They found ‘significant changes’ in colour, coating and texture in the tongues of cancerous patients compared to those without cancer.
Research at the European Journal of Integrative Medicine shows how the color and shape of a tongue reflect the health of the body.
A further resource can be found here regarding tongue diagnosis.