Interestingly, in the past there was a lot more self-experimentation done by researchers.

The history of such self-experimentation is chronicled in a book called "Who Goes First?":

https://www.amazon.com/Who-Goes-First-Lawrence-Altman/dp/052...

There's an interesting book called "Who Goes First?"[1] about something that used to be much more common than it is today: self-experimentation in medicine.

[1] - https://www.amazon.com/Who-Goes-First-Lawrence-Altman/dp/052...