972 



TERATOLOGY. 



there is one perfect heart, with some imperfect 

 part or parts of another attached to it. 



11. The eleventh group of this division 

 includes the cases of lateral duplicity, in 

 which the body is single in the middle, but 

 doubled above and below (or in brutes ante- 

 riorly and posteriorly). In these, which are 

 of rarer kinds, a single neck bears two more 

 or less completely separated heads. The 

 vertebral column is for a considerable length 

 single, but at its lower part again divides, and 

 bears two sets of lower extremities. 



12. In the twelfth group the body is single 

 above and doubled below. 



13. In this there is a tendency towards 

 singleness, or even complete singleness, of the 

 head, but all parts of the trunk and all the limbs 

 are doubled, an arrangement by which, as al- 

 ready stated, these form a series entirely dis- 

 tinct from the rest. In some of these cases 

 the two heads are found coalesced below ; in 

 others, to which the name of janiceps has 

 been given, one face is directed backwards 

 and the other forwards, the remainders of the 

 two heads being merged into one ; in others, 

 one face is perfectly, the other very dcficientli/, 

 developed ; in others there are only the indis- 

 tinct traces of a second head presented in the 

 existence of one or two ears on the posterior 

 aspect of the more perfect one ; in others, 

 this trace of duplicity is still less evident ; 

 and, lastly, in the remainder of the group, it is 

 entirely lost, and one head only, which may 

 be well or ill formed, is found upon the 

 double body. 



3. Inferior duplicity. 



My third division of double monsters in- 

 cludes the cases in which there are two com- 

 plete bodies with the lower portions of their 

 respective trunks united, so that there is a 

 head with upper extremities both above and 

 below (the bodies being placed in the same 

 straight line) and on either side of the part 

 at which they meet two lower limbs. One 

 may best conceive this arrangement by sup- 

 posing two children stuck together by theii 

 buttocks, and so fixed with wide-spreading 

 lower limbs, as may be seen mflg. H6. of the 

 second volume of this Cyclopaedia. A com- 

 mon body is thus formed with a head at each 

 end, with two upper limbs both above and 

 below, and with two lower limbs, one belong- 

 ing to each foetus on the right and two on the 

 left of the united portions. A few cases only 

 of this remarkable monstrosity are recorded ; 

 and in these the duplicity was not always 

 complete, but exhibited in some the same 

 tendency towards singleness as was noticed 

 in the others. Thus in some there were but 

 three lower extremities ; in others there were 

 but two, or two with a third ill-developed on 

 the other side : and, again, in other groups 

 there were those which have a perfect head at 

 one end of the trunk, but an imperfect one or 

 none at all at the other. 



These monsters have been known to live a 

 considerable time, their capacity for life being 

 probably owing to the separation of the hearts 

 and the absence of malformation in the more 



important organs of the body. The umbilical 

 cord is single, and never has a double set of 

 vessels ; an apparent proof (confirmed by si- 

 milar examples in other classes) that the one 

 body is not formed of the materials of two ; a 

 conclusion which is supported by the coinci- 

 dent singleness of the anus and urinary blad- 

 der, and the union of the intestinal canals. 



4. Posterior duplicity. 



The fourth chief form is posterior duplicity, 

 in which two bodies are united by their 

 backs, or a part of them. The union may be 

 at the pelvis (which is most common), and 

 occurred in the well-known Hungarian sisters, 

 who lived to their twenty-second year ; or at 

 the back of the vertebral column, or at the 

 back part of the heads. 



5. Superior duplicity. 



The fifth is the superior duplicity, in which 

 the two children are connected by their skulls, 

 the bones of which are united so as to form a 

 single skull. In these also the place of union 

 varies greatly. The frontal bone of one coa- 

 lesces with the parietal or the occipital of the 

 other, or the foreheads are attached to one 

 another, or the side of one head to the front 

 of the other. But all these are very rare, and 

 of each kind only one or two examples can 

 be found on record. 



All these are true double monsters. Of 

 tripled-badied monsters but one instance is 

 known in the human subject (Atti dell' Acade- 

 mia de Cattania, t. viii. p. 203., 1834-). 



To conclude the description of duplicity, 

 those which occur in individual parts of tlie 

 body, the rest being single, viz. in the head, 

 chest, abdomen, and limbs, ought to be re- 

 corded ; such as, for example, two mouths, su- 

 pernumerary teeth and horns, two oesophagi 

 or duodena, double hearts, or supernumerary 

 cavities in one heart otherwise well formed, a 

 double penis and urethra, a double clitoris, 

 supernumerary breasts, kidneys, vertebras, ribs, 

 fingers, toes, or whole limbs. But for all 

 these I refer to my monograph. 



At present I prefer to give all those con- 

 siderations upon the origin of double mon- 

 sters, of which this highly interesting subject is 

 capable. From all the facts I have published, 

 I point out the following generalisations: 



The double monsters form collectively one 

 class of organic beings, which, however dif- 

 ferent in their several degrees of malforma- 

 tion, may be arranged in one continued series. 

 As the lowest degree of duplicity, may be 

 mentioned that of a single part of the body; 

 for example, a double or supernumerary fin- 

 ger ; as the highest, a complete double mon- 

 ster with two heads, four upper and four 

 lower limbs, and two trunks, such as the 

 Siamese twins. And between these two ex- 

 tremes there are different forms of duplicity, 

 which gradually run one into the other. 



There is no positive or constant relation 

 between the external and the internal organs 

 as to their degrees or modes of duplicity. la 

 the completes! duplicity of the exterior, for 



