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by Peter Gwin IN MY HAND I’m holding a warm, beating heart. About the size of a softball, it’s a luminous globe of scarlet, pink, and white tissue. I can feel its chambers contracting and hear the whoosh of the fluid it’s still pumping. It’s slimy and gives off a slightly pungent odor. The organ is alive almost eight hours after I watched Paul Iaizzo remove it from a sedated pig in a basement lab, connect it to tubes simulating arteries and veins, and spark it back into rhythm with an electric jolt, as a paramedic would shock a human heart back to life..

  by Peter Gwin STEP INTO A traditional apothecary in China today and you’ll encounter rows of jars and bins filled with a colorful and aromatic array of substances—from common roots, herbs, and flowers such as ginseng, mint, and jasmine to more exotic items, including wasp nests, abalone shells, earthworms, scales of endangered pangolins, and even human placentas. For more than two millennia, traditional Chinese healers have been culling these and thousands of other ingredients from the natural world for use in medicines. But focusing on the unusual forms they may com..