Vulcan Biology (March 7, 2015)

Captain Kirk orders Mr. Spock to sickbay, where Dr. "Bones" McCoy examines him and finds that if he is not brought to Vulcan within eight days, Spock will die due to extreme stress produced by chemicals being pumped through his body. When Kirk confronts Spock, Spock says he cannot tell the cause of his problem because it is a deeply personal affair. Kirk eventually cajoles Spock into revealing that his problem is "Vulcan biology," which Kirk correctly concludes means Vulcan reproduction.