In a paper published in the "Bulletin of the Maryland Herpetological Society" in June 2007, Harvard herpetologist Van Wallach analysed 950 reported cases of snakes with two heads, a condition known as axial bifurcation or dicephalism. Throughout the ages, many variations on reptiles with two heads have been reported, Wallach wrote. In most cases, both heads have their own esophagus and trachea, and often their own heart and set of lungs, but snakes with one head and two jaws, as well as those with two heads and one jaw, have also been reported. Wallach also cites the case of a hermaphrodite two-headed snake, half male and half female, but calls this report "incredible" and unverifiable, since the specimen was lost.