Well that backfired! Remember folks, always find a way to test your science experiments (especially if it’s some kind of serum that will alter your body chemistry)!
Amazing Spider-Man (Vol. 1) #100
Published: c. July, 1971?
Cover Date: September, 1971
“The Spider or the Man?”
Writer: Stan Lee
Artist: Gil Kane
Inker: Frank Giacoia
Letterer: Artie Simek
What’s funny is that in issues with the 6-armed Spider-Man (I don’t think it’s ASM #101 but What If’s and alternate Spidey stories, he is wearing a costume where all of his arms are covered. Which means this Spidey made a new costume with 4 extra arms. That thing must be very tough to slip into.