werner@aecom.UUCP (Craig Werner) (11/16/84)
<><><><><><><><><> Transplanting a heart is relatively easy as far as connections are concerned. There are 2 veins on the right, 4 on the left, and two arteries. There are also 2 nerves (both strictly motor, no sensory). That's it. Transplanting a head is different. There are quute a few neck muscles, but that's the easy part. There is also the spinal cord. That is not easy. It contains fibers for the three cervical nerves, the brachial plexus, the seven intervetebral nerves (12 thoracic nerves in total), lumbar, and sacral nerves as well. Each one of these has a posterior and an anterior component, and each posterior and anterior component has a sensory and motor component. That's several hundred fibers, and all have to be sent down the correct myelin sheath (providing that most of them haven't been obliterated by the surgeon.) Nerves are not color-coded, in fact they look a lot like lymphatics, arteries, and veins (which also have to be connected). Therefore a head transplant will never be feasible -- and I say NEVER with much certainty. There has been very little success (some though) with reinnervation of the hand, and that only contains about 20-odd nerve branches. -- Craig Werner !philabs!aecom!werner What do you expect? Watermelons are out of season!