Life processes are similar in all animals with
backbones. So physiologists can find out a lot about
the human body by studying animals such as frogs,
rats and rabbits. Sometimes research involves the
death of these animals. But physiologists take great
care not to hurt the animals. The animals are usually
put to sleep during the experiments so they do not feel
pain. Many people think animals should not be used
for experiments. But it is only by physiological research
that medicine has been able to advance. Polio is a
disease that attacks the nerves. Millions of people have
been protected from polio by a fluid called a vaccine.
Tissue from monkeys is used to make the vaccine.