964 



TERATOLOGY. 



surrounding an amorphous mass of cellular 

 tissue, and only a single well-formed organ. 

 I have given a fuller account of this case in 

 my Tab. Ixii. figs. 4, 5, 6. Therefore we may 

 conclude that each part is formed sponte sua, 

 and that it is in its evolution quite indepen- 

 dent of the rest of the body. 



b. A less degree of malformation is when 

 the superior part of the body is formed without 

 the inferior limbs. 2*%. 59'?. gives a represen- 

 tation of this monstrosity, of which a succinct 

 account is to be found in my Handbook, D. ii. 

 Bl. 100, and Tab. Ixiii. 



c. In a more perfect developement of the 

 trunk one of the extremities may be wanting. 



We call this malformation monopodia; in 

 it one of the inferior half-parts of the body 

 has not been formed. It makes a transition 

 to those monsters, in which the inferior ex- 

 tremity of the body tapers gradually into a 

 tail-like form, which has given to them the 

 name ofmonstra Sireniformia. 



d. Sympodia or Siren -like form is the 

 fourth species of defective formation of the 

 trunk. The single inferior extremity is com- 



Ftg. 622. 



Fig. 623. 



Uromelia. 



Sympodia. 



posed of the elements of two, and arti- 

 culates with a pelvis, which is not formed, 

 as in monopodia, by one bone, but by a 

 coalescence of two. In most of them the 

 partially double, partially single inferior ex- 

 tremity terminates in a caudal point ; on 

 account of which the name of Sirenes has 

 been adopted. To this imperfection are added 

 closed anus, defect of external genital parts, 

 and the existence of but one artery in the 

 umbilical cord. The malformed inferior ex- 

 tremity has not always the same form. There- 

 fore we admit three varieties: 1. Without 

 a foot, Sirenomelia of J. G. St. Hilaire ; 2. 

 With a single foot, more or less complete, 

 Uromelia of J. G. St. Hilaire ; 3. With a double 

 foot. Fig. 622. represents the second, and 

 fig. 623. the third variety. 



By this survey of the four types of de- 

 fective formation of the trunk is proved that 

 they form a very natural series, in which we 

 are gradually inducted, from the total want of 

 a trunk to monsters in which inversion of 

 the inferior extremities is the only deviation 

 from the natural form. The same regularity 

 is here to be observed as in every other 

 class of monstrosities. It is therefore impos- 

 sible to ascribe their origin to accidental ex- 

 ternal causes. Meckel has opposed his own 



