When I was in nursing school, we studied types of cancer. A woman had an especially active cancer which the doctors took a sample of. That was back in the 1960's and they still use that sample to this day to grow more. So whenever they wanted to test a cancer treatment, they would just grow a sample from that and use that for the test.
So.... ever since I read about that, I'm rather squeamish about any "meat tissue" being grown for food....
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