When an animal suffers, humans see it as our responsibility to end this animal’s misery. This is not the case, however, when a human suffers. Why not? Because humans still have potential value while suffering. All animals are good for, according to many people, is to do work. Even pets have the job of making their owners happy. Most of the time, suffering (such as a broken leg or a tumor) makes their job significantly more difficult, sometimes impossible. Humans, however, can still be productive whilst suffering. Humans still make conversation, and sometimes still provide for their families and employers, while suffering. This, along with the moral view that a human life is exceedingly more important than an animal’s life, explains why most do not condone the killing of a human because of that human’s suffering.
However, the mercy killing of a human, should the human so desire, should absolutely be legal and condoned. No human being should be forced to suffer more than that person wants to because of the moral code of other people. Accordingly, each person should keep a will regarding what action to take in the event that this person should become otherwise incapacitated, such as slipping into a coma. Presumably, in the absence of such a will, either it would be assumed that this person wants to live, or the closest family would decide for him/her.