II. Double Monsters, in which one of the Foe tuses is more or less perfect and the other merely an Appendix to it (Heteradelphi).
Under this name of heteradelphs, which we owe to Geof•oy St. Hilaire, we understand that species of double monsters of which one foetus is large and perfect, and another, or part of another, adheres to it like a para site. They should be considered as twins, of which one has been developed at the expense of the other, which other sometimes becomes partially included in its body. According to the more or less perfect state of the appen dix, they are reduced to different species.
First Species. — The appendix consisting of a head only. — This may be connected : I. With the epigastric region (Winslow, Hesse), 2. With the cranium (E. Home), 3. With the back (Chabelard), 4. With the palate (Hofmann), or 5. With the under-jaw of the perfect fcetus (Geoffroy St. Hilaire, G. Sandifort).
Second Species. — The appendix consists of more or less developed extremities only. Supernumerary extremities, more or less deve loped, are connected with some part of the body of a perfect fcetus, as : 1. Pelvis and two inferior extremities con nected with the epigastric region of the per fect fcetus (Serres, E. Sandifort, Trombelli, Mayer, Winslow, Reschel, Buxtorff, Cantwell, Lycosthenes).
The appendix is sometimes more, sometimes less perfect ; sometimes connected with the sternum, sometimes with the epigastric region or in communication with them by a cylin drical cutaneous prolongation. In the appen dix are'regularly formed organs of generation, kidneys, an intestinal loop in communication with the intestinal canal of the supporting fcetus, and vessels which anastomose with those of the latter. The adhering parasite is therefore one with its supporter.
2. Pelvis and the two inferior extremities connected with the lateral wall of the abdo men of the perfect fcetus (W. Vrolik).
3. Pelvis and two inferior extremities con netted with the pelvis of the perfect fmtus (Ntunan, Osiander, Haller).
4. Separate anterior or posterior extremi ties connected with some part of the perfect faitus (W. Vrolik, Von Baer).
All these varieties are indicated under the names of gastronwle, pygonwle, and melomele.
Third Species. — The appendix is an ace phalus with four extremities. — The union has as yet been observed only at the epigastric re gion of the supporting feetks, through which the abdominal cavity was common to the two bodies. In the appendix the genital organs existed, but the anus was closed. In many
cases, the evacuation of urine has been ob served; the appendix showed circulation of blood ; it had its own temperature, and was dependent for nutrition on the chief or perfect body. In the interior were found uropoietic organs, vessels connected with those of the chief body, and an imperfect intestinal canal (Otto, Serres). In the supporting foetus are sometimes found traces of double organs (Otto, Serres, Rosenstiel).
Fourth Species. — The appendix a com plete body with a head and four extremities (Bartholinus).— This form of heteradelph makes the transition to anterior duplicity. The appendix has but to be more equally pro-. portioned to the chief body, and a completely double monster is formed. The best ex ample of this occurred in the person of a cer tain Lazarus Colloredo, who lived for some length of time. His portrait is given by Bar tholinus.
This very peculiar appendix never took food, nor had it evacuations of faces. But the organic and the animal life appeared to be very well developed, as its cutaneous ex halation, its movements of different parts of its body, and the fact of its sleeping, showed.
The common character, by which this whole class of heteradelphs is distinguished, consists in the comparatively smaller size, and, in ge neral, the defective developement, of the part which is termed the parasite. Imagine this difference removed by the fuller developement of the parasite, by its obtaining all its own organic apparatus, and by its growing pari passu with the other, and an exact idea of complete duplicity will be formed. It will be observed also, that in the several members of this class there is a regularly graduated series, from those in which the superfluous part is only an ill-developed limb, to those in which the parasite differs from the chief in nothing but its inferior size and its depend ence for nutrition. The cases of the last kind are, however, rare. I know but three, of which that of the said Lazarus Colloredo, de scribed by Bartholinus, is the most remarkable. Much more commonly the parasite, even when it possesses its full numerical complement of parts, bears many signs of defective develope ment ; it is hare-lipped, or a cyclops, or has atresia ani, or some other malformation from arrest of development. All this seems to me to prove, that in heteradelphs there are always the rudiments of two bodies, though one or both may be defective.