070 



TERATOLOGY. 



the other classes, examples are found of gra- 

 dations towards a state of singleness. For 

 instance, the upper parts of the body being 

 completely double, the lower are united, so 

 that there are but three limbs, or only two 

 lower or posterior limbs. And, in like manner, 

 although in many cases the bodies are alike in 

 size and other characters, yet there are many 

 more in which one has so far surpassed the 

 other, both in size and in stage of develope- 

 ment, as completely to fill up the series be- 

 tween this class and the decided heteradelphs. 

 Whilst in the latter case we find close approxi- 

 mations to duplicity, there are even among the 

 most perfect double monsters peculiarities 

 which constantly recall to mind the parasitic 

 attachment of the heteradelphs. 



With this nearly perfect external duplicity 

 there sometimes, but not always, corresponds 

 an equal duplicity of organs. The umbilical 

 cord may be single (Parsons, Otto), notwith- 

 standing the heart is perfectly double. The 

 two umbilical arteries belong but to one child ; 

 the umbilical vein bifurcates and enters both 

 bodies. In another case (Cruveilhier), the 

 single umbilical cord had two veins and four 

 arteries, and the heart was externally single, 

 and in its internal parts imperfectly double. 

 In a third double monster (Otto), the umbili- 

 cal cord had five vessels, two umbilical veins, 

 and three arteries, and in this there were two 

 hearts. In a fourth double monster the heart 

 and umbilical cord were single. The bond of 

 union, as far as the skeleton is concerned, is 

 commonly a tough fibrous connection between 

 the lower extremities of the sterna and the 

 ensiform cartilages, which are set directly 

 opposite to one another. 



The rest of the sterna and the ribs are usu- 

 ally distinct, and the thoracic cavities are 

 thereby separated. In this case there are 

 commonly two separate and perfect hearts ; 

 but in the cases in which the sterna are 

 more completely fused, or (as happened in 

 one case) entirely absent (Connn. Lift. JVo- 

 rimberg.), only a single heart, or one partially 

 double, with, for instance, two ventricles and 

 four auricles, or otherwise malformed, is found. 

 But it is particularly remarkable that in these, 

 as in all other kinds of double monsters, there 

 is no constant relation whatever between the 

 respective states of the external and the in- 

 ternal organs, for the condition of the two 

 digestive canals, even in those which are ex- 

 ternally almost alike, is subject to still greater 

 varieties than the condition of the heart. The 

 abdominal organs are always in some degree 

 connected ; the two livers are usually con- 

 tinuous. 



A spleen, pancreas, and stomach are com- 

 monly found in each body, and each stomach 

 has its own duodenum, which, after some 

 length (being continued into the jejunum) unites 

 with the other to form a single tract of small 

 intestine, which again divides into two canals, 

 leading respectively to the large intestine of 

 each body. The lungs, the urinary, and the 

 genital systems are always double. The most 

 remarkable example of this class was the well- 



known Siamese twins. When exhibited, they 

 were not exactly opposite to each other, but 

 stood side by side, or, rather, obliquely one 

 by the other ; but this position, there can be 

 little doubt, was acquired by the attempts 

 which they had instinctively made to separate 

 from each other in walking, or in lying and 

 sitting down, and by the extension they had 

 thus effected in their bond of union, which 

 was considerably more slender than in any 

 other yet described. It was quite impossible 

 for them to remain always face to face; there- 

 fore their bodies acquired an oblique direction, 

 in which they also moved. The consequence 

 of this was, that the right limbs of the one and 

 the left of the other individual were the prin- 

 cipal organs of movement ; and that the inter- 

 mediate limbs, that is to say, the left of the one 

 and the right of the other, remained merely 

 passive (Dubois). The one individual was 

 stronger than the other, and seemed to over- 

 rule him. But, nevertheless, in organic and 

 animal relation of life they seemed to be inde- 

 pendent of each other. Each had his own 

 circulation of blood, his own respiration, and 

 digestive functions. There did not seem to 

 be a large anastomosis of vessels between the 

 two bodies. But, by analogy with the fore- 

 said cases, we may conclude that these twins 

 are connected by the ends of their sterna, and 

 by some of their abdominal organs. Asa proof 

 of this connection, may be adduced the result 

 of the observations of Mr. Mayo, communicated 

 at the Conversazione of the College of Physicians 

 March Sth, 1831, that when either'of the 

 youths coughed, the bond of union swelled 

 up in its whole length, proving that they had 

 but one peritoneal cavity, of which a trans- 

 verse prolongation passed through the con- 

 necting medium. And, therefore, I should 

 conclude, that an attempt at separation could 

 not be made with probability of success. The 

 probability of having to cut through a piece 

 of liver, or a peritoneal canal, must render an 

 operation unwarrantable, unless, indeed, after 

 the death of one of the bodies during the 

 healthy state of the other. The case reported 

 by Konig has scarcely authority enough to 

 support a contrary opinion. 



2. Lateral duplicity. 



The varieties of form in anteriorly duplex 

 monsters are closely limited by the partial 

 nature of the union of the sterna and the 

 nearly complete distinctness of the thoracic 

 cavities, and hence of the whole upper part of 

 the body. In the next class, which I call lateral 

 dupliciti/, there is no such limit; and between 

 the highest degree of duplicity found in it 

 and the lowest, or that in which the duplicity 

 is most nearly reduced to singleness, there is 

 a far more numerous series of intermediate 

 forms than in any other of the types of double 

 monsters. In lateral duplicity, the two bodies 

 are not set opposite to one another, but are 

 turned sideways from one another. They 

 have a common thoracic cavity, for the forma- 

 tion of which (at least, in the highest degree 

 of duplicity,) the right ribs of one body, and 



