I think their digestive track is a bit like that of a rabbit or a rat. They cannot regurgitate so their system has to try passing anything that their system does not agree with (ie hairballs, etc)
__________________ Sophie and her bouncy furballs:
chinchillas CANNOT vomit b/c of the design of their system. The first time that question popped into my head was when I had to take one of the kids in for surgery and they didn't tell me to fast him. I asked the vet and she told me that they can't throw up.