When Paul Bert, a French physiologist, started to stitch mice together in 1864 he probably wasn’t thinking about the fountain of youth. His main interest was in animal grafting; the way tissue transplants could survive away from the body and affect a biological system (1).
Bert’s successful attempts in parabiosis, the surgical joining of two entire living animals, should establish whether tissue grafts from one animal could also be used on the joined animal and what the immunological implications were. Besides, this experiment also proved that blood from one mouse circulated freely into the other mouse and an “extended physiological and pathological connection result[ed] from the vascular connection”.
About 150 years later, these experiments are once again picked up by scientists. But this time they inspire a whole new scientific discipline: the understanding of aging.