I described the various kinds of terata in _Essays in Pastoral medicine_,[58b] and of these the most important in the matter under discussion here are the double and triple monsters. Many of the double monsters evidently were two persons. There is only one well authenticated case of a triple human monster, and this happened in Italy in 1831. It had a single broad body with three distinct heads and two necks, and was killed in delivery. There is no proof as to whether it was one or more persons. The standard of judgment in such cases as regards the presence of one or two souls in the monster is the evidence of one or more distinct consciousnesses. A monster double from the navel or breast downward (_terata anadidyma_) is, I think, one person. There was an example of a monster in this group which was divided from the foreheads downward; or better, the distinct twins were united by their foreheads only; but such a form is very exceptional. In my article on "Human Terata and the Sacraments," in _Essays in Pastoral Medicine_, in 1906, I expressed the opinion that a monster which is single to the navel and double below is composed of two persons, but I now am of the opinion that such a monster is only one person, because there is apparently only one consciousness. There are about eight cases of two-headed monsters known which were evidently two persons in each case, and several terata kata-anadidyma, divided above and below but joined at the sternum, abdomen or sacrum. Several ischiopagic twins, joined at the pelvis with the heads at the opposite ends of the double body, are grouped with either the katadidyma or kata-anadidyma. It is commonly not difficult to recognize individuality or duality of personality in monsters, but it is not easy to explain the origin of life, to point out the moment the _second_ soul enters these fused or undivided twins. [58b] Chap. vi, p. 69. New York, 1906. We can artificially obtain double embryos of frogs by inverting the blastomeres in the two-cell stage.[58c] We thus get united twins with heads turned in opposite directions, twins united back to back like the Blazek Sisters, twins united by their ventral sides, and double-headed tadpoles, but we have no knowledge of how similar doubling in human monsters takes place; we must guess vaguely from analogy. There was one soul, at least, present from the one-cell stage of the human monster; when the second soul is created and infused we do not know, but the moment of the creation of this second soul has no practical significance in this discussion. [58c] See Wilson, _op cit._., p. 421.