(Long after the fact, so probably missed the boat. Also, I'm Not An Expert on This, so grains of salt, etc.) My understanding of Mad Cow was that the prions i

(Long after the fact, so probably missed the boat. Also, I'm Not An Expert on This, so grains of salt, etc.) My understanding of Mad Cow was that the prions involved were ones which were allowed to pass the blood/brain boundary, which keeps arbitrary chemicals in food from having a big effect on our neurological state. (Drugs like MDMA imitate certain chemicals used by the brain and are thus allowed to pass by.) One of the reasons cannibalism - especially when brains are involved - is that the brain proteins look like your brain proteins, and are thus expected to be on the 'brain' side of the boundary. So when cows eat dead cow brains, they get serious neurological diseases, just like human cannibals are known to. Prions may be arbitrary bad proteins, but they're especially problematic in the case of eating brains.