Somatotype and constitutional psychology

Somatotype is a taxonomy developed in the 1940s, by American psychologist William Herbert Sheldon, to categorise the human physique according to the relative contribution of three fundamental elements, somatotypes, named after the three germ layers of embryonic development: the endoderm, (develops into the digestive tract), the mesoderm, (becomes muscle, heart and blood vessels), and the ectoderm (forms the skin and nervous system). His initial visual methodology has been discounted as subjective, but later formulaic variations of the methodology, developed by his original research assistant Barbara Heath, and later Lindsay Carter and Rob Rempel are still in academic use.