Rh

A basin of blood sitting on the floor. The same one used for washing. Nobody thinks to dip their hand in and spread some over the farmhouse door, warning the Angel of Death to stay away, not to come for this child. Nobody gets down on their knees to pray. They already know they are cursed. It is 1931. It is the fourth child to have died.

Lucy lies in the bed, lies on her side while the neighbor’s wife cleans her legs and backside with Lysol. It does no good. All Lucy can smell is sweat and dried blood and her own bowels turned inside out. In her humiliation, she won’t speak. She doesn’t need to. God is broadcasting her sins. Her husband is already back in the field, counting his own transgressions. Like the Aztecs, they do not understand why the sun rises. To retain the order of things, a sacrifice is required.

The neighbor’s wife wraps the dead child in a dish towel. At the same time, on the other side of the country, a melancholy man of science worries over his microscope. He is observing what happens when the blood of a rat is injected into the blood of a rabbit. Blood is all Karl Landsteiner has thought about for years. That and the piano, which he played in the evenings until his neighbors complained that they couldn’t hear the radio. Americans, he says.

This is what the lord says: “Every firstborn son in Egypt will die, from the firstborn son of Pharaoh, who sits on the throne, to the firstborn of the slave girl, who is at her hand mill. . . . There will be loud wailing throughout Egypt—worse than there has ever been or ever will be again.”

For Lucy, the Lord has turned it on its head: her firstborn thrives. The child is helping her grandmother make bread across town and waiting to hear if her half sister or brother is alive or dead. She hopes this one is alive and is a girl, but she’ll take either. She just wants someone to scold when she’s playing school. She just wants something to hold like a doll.

Lucy believes her misfortune is all because of this first child, who grew in her belly like a magnet pulling some things closer and pushing others away. This child is the daughter of a man long gone. Lucy is right, but not in the way that she thinks. When that baby came, she was drawn out into the world with such exuberance. The sound of a ticking clock kept time with their shared pulse, and as the baby rushed forth, her blood mingled with her mother’s—a parting kiss.

This is what landsteiner says: “Owing to the difficulty of dealing with substances of high molecular weight we are still a long way from having determined the chemical characteristics and the constitution of proteins, which are regarded as the principal constituents of living organisms.”

In his lab in New York City, Landsteiner’s dog Waldi whines in his sleep. Landsteiner is an old man. He has done more than a lifetime’s worth of work, classifying human blood into types—A, AB, B, and O—for which he received the Nobel Prize. He has discovered the polio virus and demonstrated the existence of antigens. He has lived through a world war and made it to America and been given a son in his old age. But there is one last thing he must do.

Waldi barks, reminding him that it is lunchtime, and Landsteiner reprimands him. Waldi, he says, you’ve not an atom of respect for science. But they both know Waldi is science. The proteins in his animal blood, his base needs and base joys. Waldi knows why the sun rises.

Landsteiner and his colleague Alexander Wiener wait until 1940 to publish the results of their experiment injecting the blood of a rhesus monkey into rabbits and observing a new immune reaction—owing to an undiscovered protein on the red blood cell. They will call it the Rh (rhesus) factor and...