Scientists say they’ve discovered a new organ — possibly the human body’s largest — and it was hiding in plain sight, according to a new study. The so-called interstitium is an interconnected system of tiny fluid-filled cavities throughout the entire body that acts as a “highway” for our internal water supply, study co-author Dr. Neil Theise told LiveScience.com. The findings were published in the journal Scientific Reports Tuesday. The human body is 60 percent water, and while two-thirds of that liquid remains inside cells, the remaining water — called interstitial fluid — is free to move throughout cavities inside the...