In humans, the same primitive area of the brain stimulated by food or sex is also stimulated by acts of altruism. 人类大脑中受食物和性刺激的脑区也受利他主义行为的刺激。
The sex organs and the mouth are the two most easily stimulated erogenous zones of the body, and it is therefore only natural that they should be brought into direct contact. 性器官与口腔是身体的两个最容易刺激的性敏感区，因而打开头就应该让它们直接接触是再自然不过的事情了。
