A true triple monster in which there has been first a duplication of the one extremity, and then a second duplication of one of the parts, is very rare. In one authentic case there were three heads (Triceph-alus), two of which were on a single vertebral column, the cervical vertebrae being alone divided, while the other had a separate column to itself. A case of triplication in which two of the foetuses were parasitic is also recorded. The remains of one foetus was in the abdominal cavity, and that of the other was appended to the perineal region. (See Foerster, Missbild).