Killing animals for bioassays is a central task in many life science research projects, and doing so is a routine part of lab life in a number of working groups. But when students are first confronted with the reality of killing experimental animals, many feel sympathy for the creatures, uncertainty, and pangs of guilt. How do young scientists deal with these feelings? Peter Ansari, Ph.D., a student in the Johannes Mueller Institute for physiology at Berlin's Humboldt University in Germany, asked some of his fellow students.

"In the beginning it was very hard for me to kill animals for my experiments. But with time I got accustomed to it. Actually, I do not concentrate on dispatching any longer," says Claudia. She devalues the process of killing to a purely mechanical affair, which is not connected with any reflection, a strategy adopted by most of the people employed in this field.

There is a practical reason for this, too. "In my experiments I need fresh brain tissue," says Roland, a student in Berlin. "It is therefore mandatory that the slaying goes fast and the brain is removed briskly. If I thought about each experiment, I could not operate that fast and would probably make errors."

Students are more likely than senior scientists to feel pangs of guilt, but everybody who deals with bioassays emphasizes that they don't enjoy killing lab animals, although the guilt threshold with insects is surely lower than that with mammals.

Bioassays are performed on almost all species of animals, from threadworms and insects to snails, frogs, birds, rats, and apes. Slaying a grasshopper or killing a bee or a fly for an experiment does not trouble most scientists. It is not quite clear whether the reason for this is in the remote relationship or because of the absence of blood and visible pain symptoms. Even the legislature considers this and requires nothing more than an announcement for experiments with invertebrates. Experiments with mammals, on the other hand, must be described in detail, and the reason for the experiment has to be justified. Thus research on apes has become almost impossible in Germany.

Scientists differ in the strategies they use to cope with the strong feelings that can be engendered by killing laboratory animals. In the long run, some become cynical. "I don't feel bad about killing rats for experiments. Considering everything that is killed otherwise, it is only a small contribution. Much is slaughtered and not eaten or simply run over."

Others concentrate on the experiment and reflect rather factually over the killing: "I start the actual evaluation of the killing at the end of the lab day. The process of killing is unkind to me, but anyhow I don't try to perceive the animal as a subject," says Katharina. "If, however, the experiment fails and no usable data were produced, I feel sympathy for the animal."

Although the search for substitutions for animal experiments has achieved some success over the past few years, and methods such as cell cultures can reduce the number of laboratory animals that are killed, obtaining answers to some biological questions will still require sacrificing animal lives. The bioassay, including killing, will therefore remain a part of the researcher's everyday life and will force scientists to reflect constantly on the necessity and value of each experiment.