"firm but gentle" control of children. He warns against self-demand feeding, a type of feeding that had become popular in the 1940s. Because parents were letting their baby dictate when he or she should be fed, some parents began indulging all of their child's desires, resulting in unregulated sleep schedules and a loss of control for the parents. Spock clarifies in his manual that while parents should respect their children, they also must ask for respect in return. By the fourth edition, Spock adapts to society's shifting ideas of gender equality, especially after the rise of the women's liberation movement and concurrent feminist criticisms about sexism apparent in Baby and Child Care. Spock changed every pronoun for the baby, previously referred to only as "he", and discusses ways for parents to minimize gender stereotyping while raising a child. He warns against praising girls only on their appearance and notes the sexism present in a household where girls learn to do housework while boys play outside. Spock also continues to expand on the role of fathers and acknowledges that parents should have an equal share in child-rearing responsibilities, while also both having the right to work. In the seventh edition, Spock endorses a low-fat, plant-based diet for children due to rising trends in obesity and Spock's own switch to a macrobiotic diet after facing serious health issues. Reaction Within a year of being published, The Common Sense Book of Baby and Child Care had already sold 750,000 copies, mostly by word-of-mouth advertising. Mothers appreciated that Spock was not condescending in his writing and instead very empathetic towards mothers, acknowledging how tiresome child care can be. Although he believed that much of a child's personality and behavior rested in the parents' hands, he did not scare parents with this large responsibility of raising a "good" child, like earlier child care experts had. He was lauded for writing with a friendly, reassuring tone and using conversational, easy-to-read language. Spock was popularized by mentions in household magazines and famous television shows, such as I Love Lucy, where the characters Lucy and Ricky Ricardo were seen consulting Spock's manual in various episodes when seeking advice for raising their child. Spock quickly became a household name in the 1950s and is frequently credited for helping to raise a generation of "Spock babies" in the post-war period. Mothers heavily relied on his advice; by 1956, The Common