Your Majesties, your Royal Highnesses, ladies and gentlemen; on behalf of Shinya Yamanaka and myself, may I express our profound gratitude to the Karolinska Institutet and to the Nobel Foundation for this pre-eminent honour bestowed on us at this time.

Shinya Yamanaka and I must be more different than any other previous co-recipients of the Physiology or Medicine award. Shinya Yamanaka was born in the year of my main finding, and we have never worked together or on the same material; yet we share our great wish that our contributions may help to alleviate human suffering in a similar way.

For my part I have worked all my life with eggs and embryos of frogs. Compared to other small animals, these have figured prominently in the world of literature. They served as a chorus in a play by Aristophanes, The Frogs, which won first prize when first performed in 405 BC. A.A. Milne’s Toad of Toad Hall was a very benign Lord of the Manor in his river community. Hilaire Belloc wrote,

“Be kind and tender to the frog,
and do not call him names.
A shiny skin, a Polly‐wog,
or Gape‐a‐grin, a toad gone wrong,
The frog is justly sensitive
to epithets like these.
No animal will more repay
A treatment kind and fair.”

I myself have been a major beneficiary of the view that no animal will more repay treatment that is kind and fair.

Shinya Yamanaka’s work has involved mice and human cells, and advances the prospect of providing new cells or body parts for patients. This concept goes back in history for a long time. The earliest example known to me, of replaced body parts, is exemplified by a Mayan skull, dating back to 1400 BC. In this skull, false teeth made of stone, had been implanted. This was not just to improve appearance in the presumed after-life. The reaction of the jaw-bone showed that the false teeth had been hammered in in life. (Perhaps, at that time, an extract of the coca tree, of South America, now used by dentists as novocaine, had already been discovered.)

Although body part replacement is not a new concept, the practice of reversing the process of cell differentiation to an embryonic state to form new cells of different kinds has become a realistic prospect during the last half century. This raises the possibility of giving people new cells of their own genetic kind, and hence, without immunosuppression, to replace cells worn out by age or disease, a hope of the new field of regenerative medicine.

Starting in my case with no therapeutic benefit in sight, we are truly grateful to our immediate families and close colleagues, Ron Laskey for me and Kazutoshi Takahashi for Shinya Yamanaka, for their selfless co-operation and support.

We thank our hosts immensely for this truly unique experience provided by a spectacular week, and also for this magnificent banquet.