Drs. Grace and Ogden both mention the case of Phineas Gage, who suffered a traumatic brain injury when an iron rod was driven through his entire skull, destroying much of his frontal lobe. He miraculously survived the accident but was so changed as a result that many of his friends described him as an almost different man entirely.
When Murdoch is teasing Crabtree about his Haitian zombie theory, Murdoch uses the word "bocor". A bocor is a malevolent witch doctor or sorcerer of Haiti. The term comes the Haitian Voudo religion (the spelling "voodoo" being deprecated).
This episode takes place in 1901.
The procedure Dr. Ogden & Dr. Grace discover is being performed on the men, is known as a lobotomy. A lobotomy is a type of brain surgery that involves severing the connection between the frontal lobe and other parts of the brain. Lobotomies became popular in the 1930s as a treatment for certain mental health conditions. Doctors performed this procedure on people with conditions such as schizophrenia and depression. At the time, there were no effective or widely available treatments for these conditions. However, lobotomies are dangerous. They carry several serious risks, including seizures and death. Due to the impact of this procedure on people who were lobotomized and their families, it fell out of use in the 1950sTrusted Source, according to 2013 research.