Carus typology was developed by Carl Gustav Carus, it classifies the body constitution into the cerebral, athletic, phthisic, phlegmatic, and sterile type. The cerebral type usually has a large head as compared to his body and is thin. He is more of a thinker and an introvert. The athletic type has broad shoulders and a muscular body. He is often active and aggressive. The phthisic individual is typically flat-chested and extremely thin as if having a wasting illness. The phlegmatic type is characterized by a lethargic and apathetic personality; and the fifth is called the sterile type. Descriptions of this "sterile type" appears to have little documentation regarding it.