At this bench, you can perform an experiment first done by Frederick Griffith in 1928. Griffith was working with an organism that causes bacterial pneumonia: the Pneumococcus (now called Streptococcus pneumoniae). His test subjects were mice. He was trying to develop a vaccine. Two common strategies for making a vaccine are to use a less dangerous strain of the infecting organism, or to use the killed organism. In either case, the immune system may be able to attack some feature of the less dangerous or dead cells. Having "practiced" with these less dangerous cells, the immune system is then able to react quickly enough to kill the more dangerous organism when it is encountered. Griffith had two strains of Pneumococci: S strains: S strains produced a sticky carbohydrate capsule or coat around the cell. When these strains were injected into mice, the mouse's immune system could not get past the capsule to attack the cells, and the mice would die from bacterial pneumonia. However, if the cells were heated, they died and could not set up an infection in the mouse. The capsule material alone did not make the mice sick. R strains had no carbohydrate capsule. When these strains were injected into mice, the mouse's immune system could successfuly attack and destroy the invading cells. The injected mice would remain healthy. Examine the different strains of bacteria in the test tubes, and inject them into the mice to observe the effect that each has on the mouse. You can "inject" each mouse by clicking on the mouse that corresponds to each of the bacterial strains in the test tubes. After you have completed the experiment, read the notecard delivered by the cage of mice, called "What is going on here."