brain was something that needed samples taken it would not leave the morgue with the body.

It takes a few days of being fixed in formaldehyde before the brain can be appropriately dissected into samples to be processed and made into microscopic slides for diagnosis. If it was deemed necessary and the family did not want to wait for all of that to be returned to the body before they took it for the funeral then I can fully understand that.

We'd have a dozen brains still on the shelves months after the bodies had left the morgue and been buried. After necessary retention times they would be sent to be incinerated.