ARREST OF DEVELOPMENT. 57 



abdomen is very defective ; the rectum is usually absent, and the 

 colon is greatly enlarged and terminates in a blind extremity. 

 The posterior extremity of the axis is curved back, and has marked 

 indications of arrested growth. The innominate bones are fused 

 below as far as the acetabula, and the femora, when present, are 

 rotated outwards until the knees look backwards; hence the limbs 

 are fused by their external aspect. The lower extremities of the 

 femora may be united into a single symmetrical bone ; the tibiae 

 are usually fused into a single bone, which may either terminate 

 in a blunt stump or support a compound foot, consisting of more 

 or less of the normal pair united by their outer sides, with the 

 heels turned forward. The united limbs are usually curved, so 

 that they are concave in front. The term sympodia has been 

 used to designate this condition ; foetuses so malformed are said 

 to be syreniform. Sometimes one limb is entirely or partially 

 wanting. When it is wanting or inconspicuous, the term mo- 

 nopodia has been used ; the developed limb is usually rotated 

 as in sympodia. 



a. Sympodia. 



228. A Human male foetus at about the seventh month of ges- 



tation, with defective development of the posterior ex- 

 tremity of the axis, with rotation and fusion of the lower 

 limbs. The foot is formed of the inner portion of both 

 feet, and presents four toes, the two inner toes of each 

 foot. The external sexual organs are extremely defective. 

 The abdominal cavity has been laid open to show the di- 

 lated condition of the colon. 



229. A similar foetus in which the fused posterior extremities 



terminate in a two-lobed stump. One lobe is turned 

 back laterally ; it is considerably longer than the other. 

 Presented by J. Stringfield, Esq. 



230. A similar foetus in which the fused limbs ended in a single 



rounded stump. The limb has been dissected to show 

 the arrangement of the muscles. The external vasti form 

 a single muscle behind ; the sartorii are straight, and run 

 down the outer sides of the stump. The two long ad- 

 ductors are close together in front. The tibia terminates 

 in a long blunt cartilaginous point. 



