DEVELOPMENTAL HAZARDS OF HUMAN TWINS 145 



of plethora are : first, a general development naore nearly 

 normal than that of the injured twin; second, a height- 

 ened blood pressure in the venous system. Some 

 secondary results are: a general oedematous and drop- 



FiG. 51. — Another typical common placenta of a pair of one-egg 

 human twins in which the vascular anastomoses, forming the so-called 

 "third circulation" is extensive, though not greatly unbalanced. Even 

 this degree of imbalance had very serious consequences on both twins. 

 (After Schatz.) 



sical condition of the body, the umbilical cord, and the 

 placenta; hypertrophy, followed by atrophy, of the liver; 

 more or less marked hypertrophy of the entire heart, 

 which becomes not only relatively larger than that of 

 the injured twin, but positively larger than those of 

 single fetuses of similar size; hypertrophy of the left 

 ventricle, observable in new-born twins: heightened 



