Mengele promoted medical experimentation on inmates, especially dwarfs and twins. He is said to have supervised an operation by which two Gypsy children were sewn together to create Siamese twins; the hands of the children became badly infected where the veins had been resected. (Snyder, Louis. Encyclopedia of the Third Reich Marlowe & Co., 1997.)
Cohen tells us:
"The only firsthand evidence on these experiments comes from a handful of survivors and from a Jewish doctor, Miklos Nyiszli, who worked under Mengele as a pathologist. Mengele subjected his victims - twins and dwarfs aged two and above - to clinical examinations, blood tests, X rays, and anthropological measurements. In the case of the twins, he drew sketches of each twin, for comparison. He also injected his victims with various substances, dripping chemicals into their eyes (apparently in an attempt to change their color).
He then killed them himself by injecting chloroform into their hearts, so as to carry out comparative pathological examinations of their internal organs. Mengeles purpose, according to Dr. Nyiszli, was to establish the genetic cause for the birth of twins, in order to facilitate the formulation of a program for doubling the birthrate of the Aryan race. The experiments on twins affected 180 persons, adults and children.
Mengele also carried out a large number of experiments in the field of contagious diseases, (typhoid and tuberculosis) to find out how human beings of different races withstood these diseases. He used Gypsy twins for this purpose. Mengele's experiments combined scientific (perhaps even important) research with the racist and ideological aims of the Nazi regime. which made use of government offices, scientific institutions, and concentration camps.
From the scanty information available, it appears that his research differed from the other medical experiments in that the victims death was programmed into his experiments and formed a central element in it" (Encyclopedia of the Holocaust, Vol. 3, p. 964).