99 Essays on Infinite Lifespans   Raymond Kurzweil its own movement, the engineering issues of the extreme pres- sures required for centralized pumping can be eliminated. As we perfect the means of transferring nanobots to and from the blood supply, we can also continuously replace the nanobots comprising our blood supply. With the respirocytes providing greatly extended access to oxygenation, we will be in a position to eliminate the lungs by using nanobots to provide oxygen and remove carbon dioxide. One might point out that we take pleasure in breathing (even more so than elimination!). As with all of these redesigns, we will certainly go through intermediate stages where these tech- nologies augment our natural systems, so we can have the best of both worlds. Eventually, however, there will be no reason to continue with the complications of actual breathing and the requirement of having breathable air everywhere we go. If we really find breathing that pleasurable, we will develop virtual ways of having this sensual experience. We also won’t need the various organs that produce chemi- cals, hormones, and enzymes that flow into the blood and other metabolic pathways. We already create bio-identical versions of many of these substances, and we will have the means to routinely create all biochemically relevant substances within a couple of decades. These substances (to the extent that we still need them) will be delivered via nanobots, controlled by intel- ligent biofeedback systems to maintain and balance required levels, just as our ‘natural’ systems do today (for example, the control of insulin levels by the pancreatic Islet cells). Since we are eliminating most of our biological organs, many of these substances may no longer be needed, and will be replaced by other resources that are required by the nanorobotic systems. It is important to emphasize that this redesign process will not  be  accomplished  in  a  single  design  cycle.  Each  organ and  each  idea  will  have  its  own  progression,  intermediate designs, and stages of implementation. Nonetheless, we are