At the end of the 19th century, scientists generally recognized that the number of neurons in the adult brain (roughly 100 billion) did not increase significantly with age, giving neurobiologists good reason to believe that memories were generally not the result of new neuron production.
在19世纪末，科学家们普遍认为成人大脑的神经元的数量（约1000亿个）不会随年龄增长而显著增加，因此神经生物学家一般都相信记忆的形成并非神经元增生的結果。