Board Thread:General Discussion v2.0/@comment-24833746-20151116053145/@comment-27200107-20160328034732

PhoebeTsumiki wrote: Juku Ren wrote: its not blood he's a skeleton Skeletons DO in fact contain blood. Red marrow, which creates blood cells, is found in several bones in the human body, such as the skull, the sternum (breastbone), femurs, and hips. Sans is cut on his sternum in the genocide run, so he is most likely bleeding blood. Also, an average adult only has red marrow in those bones, but an adolescent or child has red marrow in most of their bones.

Yeah, I agree.