I would guess that the experiment wouldn't be permitted to prolong the animal's life in such an admittedly abnormal state, since the surgery might be regarded a

I would guess that the experiment wouldn't be permitted to prolong the animal's life in such an admittedly abnormal state, since the surgery might be regarded as a form of unusual cruelty in and of itself. It was probably classified as a "non-survival surgery" and a "painful procedure without the use of pain-relieving drugs", since they would be permitting the monkey to re-awaken and test its senses in a lucid state, after a surgery in which they were uncertain of whether the monkey would live. An animal protocol like that usually anticipates euthanasia, after the basic science of the experiment has been satisfied. Since the surgery (and subsequent resuscitation) is the experiment, and it's not a longitudinal quality-of-life study, I doubt they planned retaining the monkey much more than a week after surgery.