The Avengers, Vol. 1 #140 (1975)

A Journey To The Center Of The Ant
Hank Pym collapses, his life endangered due to his microbial infection. There is good news, though: he collapsed in front of the Beast, his newest teammate, who also happens to be something of a brilliant biologist. The hairier Hank soon goes to work on the hunt for a cure, while Dr. Don Blake lends his expertise to Jan's case.
Release Date: 1975