murrskeez: This never stops being amazing to me. Our existence hinges upon the repetitive contraction and relaxation of this one mass of muscle and connective tissue.

murrskeez: This never stops being amazing to me. Our existence hinges upon the repetitive contraction and relaxation of this one mass of muscle and connective tissue.

tags: ,

from: https://melanyguerra.tumblr.com/post/103603489655