Here's a picture of Brainless: a microscopic section through the head of a salamander who, some two months prior to having been pickled, had donated its brain, except for the medulla oblongata, to another debrained animal. The cells you can see packing the cranial cavity are mainly connective tissue elements; they wandered into the void, as they would into any wound, and represent part the body's repair process, at which the highly regenerative larval salamander has no earthly peer. As Brainless shows, though, the debrained salamander does not regenerate a new brain (as it would an arm or leg).
Brainless' body did have a spinal cord, which, with the medulla, mediated reflexes; if its feet touched the surface of its dish, Brainless could stand up. But for the rest of its life, the animal was behaviorally inert. For instance, if it fell over on its side (thus removing the sensory input for the plantar reflexes), there it stayed for hour on end, until the experimenter intervened.
Obviously, Brainless couldn't learn nor reveal memory or the rudimentary thoughts of salamanders. This is not to say that a brain, as such, is absolutely necessary for remembering (bacteria, for instance, can learn) but merely that to show the world a salamander's tricks, the beast needs to have a brain inside its head.
Force-feeding a couple of times a week (on fresh fillets of salamander muscle and frog embryos) kept Brainless well nourished. A larva, the animal would ordinarily have undergone metamorphosis. But specimens of this type did not. Why? The operation took away the necessary pituitary gland, which hangs from the underside of the brain, and whose intermediate lobe puts out hormones that orchestrate the transformation from a fish-like aquatic creature to a landlubber.
Brainless and a group like him were controls (against brain regeneration) for experiments into the converse of the condition: the effects of transplanting the brain not only to another cranium -- or even of a different species -- but to a locale remote from the head.
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