He devised the first principle of mass action, stating, "As long as not too much of the lobes is removed, they may in due time regain the exercise of their functions.
"[citation needed] He also developed the theory of equipotentiality, stating, "All sensations, all perceptions, and all volition occupy concurrently the same seat in these organs.
"[2] Karl Lashley's most famous research was an attempt to find the parts of the brain that were responsible for learning and memory traces, a hypothetical structure he called the engram.
[citation needed] There are, however, examples of highly specialized areas of the brain in which even small amounts of damage can cause dramatic effects on people's abilities to perform certain tasks.
[citation needed] It is now believed that Flourens may have removed more than just the parts of the hemispheres that he claimed because his experiments can be replicated without his same drastic results.
However, there have been some functions that are believed to be contained within specific areas of the brain (many related to speech, which was impossible to determine when the mass action principle was theorized, as experiments historically only used animals).