Answer: Chemotherapy
Explanation: Chemotherapy is the use of chemical substances to treat diseases,most of the drugs used to treat the diseases of Humans were developed through animal research. The drugs for Leukemia (cancer of the blood forming tissues,bone marrow and the lymphatic system) helping in treating children battling with Leukemia where developed through animals some of the used in drugs research are Mice,White Rats etc most of which have similar biological/physiological composition like man.