A comprehensive statement on the anatomy and physiology of hatha yoga ought  to have been written years ago. But it hasn't happened, and my aim is to remedy the deficiency. After considering the subject for twenty-five years, it's clear that such a work might well interweave two themes: for the benefit of completeness, a traditional treatment of how to do yoga postures (yoga asanas) using anatomically precise terminology, and for correlations with medical science, an objective analysis of how those postures are realized in some of the great system of the body.