ampule inside will be broken, releasing the previously sterilized radioactive medium onto the lines.
Both the test and control Gullivers will be inoculated with soil simultaneously, as described above, but the control instrument will be injected with a metabolic poison soon after inoculation. The purpose of this step is to make sure that any carbon dioxide evolution that is detected is of biological origin. If space is available for more than two Gullivers, the nature of the antimetabolite can be varied so as to provide information on the chemical sensitivity—and therefore on the chemical nature—of Martian life.
In principle, Gulliver is capable of performing many different kinds of metabolic and biochemical experiments. For example, a modified version of the current model would be able to detect photosynthesis by measuring the effects of light and darkness on the evolution of carbon dioxide. This application of Gulliver has been demonstrated in the laboratory. It is important 
Figure 13.—A working model of Gulliver, tested under a variety of conditions.
