When one species mates with another, the resulting hybrids typically die or fail to reproduce. Hybrids can form between similar species from microorganisms to mammals, with the mule being a classic example. Sterile offspring of horses and donkeys, mules are prized for being more agile than the former, less obstinate than the latter, and smarter than both. But researchers prize hybrids for an ad...

Since the work of Boorman, Dodd and Trinick (1949), incompatibility in the ABO system has been recognized with increasing frequency as a cause of haemolytic disease. Robinson, Phillips and Prystowsky (1951), Shumway, Miller and Young (1955), Davidsohn (1956) and others have written on this condition. And yet haemolytic disease due to ABO incompatibility is much less widely known than that due t...