Surname Saturday: Mary Slatter, Melancholy and Demented?

Last month, I wrote about discovering in the Banstead Asylum records a woman named Mary Slatter who was possibly my husband's great-great-grandmother. I was doing a Genealogy Go-Over and learned that more records had become available, so I dove in.

The only way to find out more was to see these records in person, since they're not available in any other format. My wonderful cousin Anna in London was kind enough to visit the London Metropolitan Archives, where she read the admission and discharge registers.

If this was indeed Mary Shehen Slatter, her life was even sadder than the family could have imagined. Get out your hanky. Here's what the records say:

• Mary was admitted to Banstead Asylum on September 28, 1877, at age 40. (This is within a year or two of the age I would expect her to have been at that point.) She was married, the wife of a laborer, and she was from Whitechapel (these facts fit exactly with the Mary Slatter I'm trying to find).
• Mary's "previous place of abode" was--oh, dear--Colney Hatch Asylum. In other words, she was institutionalized before she even got to Banstead. Colney was notorious, another place to hold paupers, originally meant to be more humane but then resorting to straight jackets and other restraints. Wait, there's more.
• Mary's form of mental disorder was characterized as "Melancholy and demented." 
• Mary's cause of insanity was described as "Misfortune and destitution."
• The duration of Mary's previous attacks of insanity was 3 years, 4 months.
• Mary died young of phthisis--meaning tuberculosis--on April 19, 1889, at age 52.

Now my cousin is going to view the Colney Hatch records in person to try to learn more about whether this is indeed our Mary Shehen Slatter.

From what I know about hubby's g-g-grandmother, this could very well be her sad fate. The family was chronically impoverished, I have confirmed from the records and from later comments made by Mary's children as adults.

Mary's first-born child, Thomas John Slatter, didn't live to the age of 11. He was born in 1860 (see him in the 1861 UK census excerpt here, with the Slatter family listed in Whitechapel) and he died sometime before the 1871 UK census. * Was this why Mary was first institutionalized?

I hope the Colney Hatch records will give me more insight into Mary's life. Also, I've sent for Mary Slatter's death cert to see what it says. UPDATE: Mary's death cert is a single line in a ledger. It says "date of death is April 19, 1889; place: "Middlesex Lunatic Asylum, Banstead; female, age 52, wife of a labourer, Whitechapel; cause of death is phthisis." No place of burial mentioned, no maiden name. Since the Mary I'm seeking was the wife of a labourer in Whitechapel, the death cert supports my theory but doesn't prove that Mary Slatter in Banstead was Mary Shehen Slatter, hubby's g-g-grandma.

* Elizabeth, in a comment below, notes that Thomas seems to be alive and living with his grandparents in the 1871 census. Thanks to her help, I have clues to dig deeper!