Micnet and bitnet,do you know them?

I like old stuff of 80 and 90's and sometimes i like to study old technologies(some of them still used..) like SYSTEMV,SCO-UNIX,Xenix,etc.. Reading a book about Sco Unix on a page i see.. mail support uucp and networks like bitnet micnet and internet I know internet and uucp,but what are/was bitnet and micnet?