On: Transplanted human brain-tissue takes root in mice without a cortex

A morning paper tells me that human brain tissue, transplanted into mice born without a cortex, has taken root and knit itself into the host. The little creatures carry a piece of us in their skulls now, and the piece appears to be working.

My first impulse is the physiologist’s: this is a fine instrument. One organoid in a dish is a curiosity; a graft that integrates, vascularises, receives signals - that is a platform on which therapies may be tested before a single patient is exposed to risk. I spent a good part of my career arguing that obstetricians were carrying death from bedside to bedside on their unwashed hands, and the profession called me a slanderer for a decade. Why? Not for want of evidence. For want of willingness to look. A laboratory method that lets us collect many cases in living tissue, rather than one tragic case at a time in a lying-in ward, is precisely the discipline my critics lacked.

And yet I feel the old unease stir. Where does the graft end and the animal begin? If human cells integrate extensively into a creature’s brain, at what point does the creature acquire claims we have not granted it? I have no answer, and I distrust anyone who offers one quickly. The right course is the one the profession has always found hardest: name the discomfort before it hardens into denial, and let the question travel alongside the experiment rather than behind it.

Also noted, with a dry smile: a machine now masquerades as a corresponding author, answering letters on a scientist’s behalf. I wrote my essays at the breakfast table precisely because conversation keeps a man honest. Deputise the conversation to a contrivance and I wonder what honesty remains to keep.

A day of wonders, then, and of warnings. Collect the cases. Question the comfortable. Wash your hands.