In this case (Fig. 3) also we have degrees of duplication varying from cases of two heads on one neck to those in which the body is also to a large extent doubled. The condition of the arms indicates approximately the extent of division of the spinal column; hence we have as varieties in different stages, cases with two arms (Dicephalus dibrachius), with three arms (triorachius), and with four arms (tetrabrachius). There are even cases in which an additional lower limb has been present in a rudimentary state (Dicephalus tripus), the duplication having extended almost.throughout.

These forms are very common, forming indeed the most frequent double monsters. The malformation causes great difficulty in parturition, but, if safely delivered, the monster is quite capable of life, and may even attain to old age.