The cerebrum is the center of will power, consciousness and memory. In other words, it is one of the most sensitive areas of the brain and many of the reactions of the inner senses like anger, fear, etc. relate to it.
If we take out the cerebrum in an animal but we leave the other organs as they are, it will remain alive but its understanding and consciousness will be totally eliminated.
They have removed the brain of a pigeon. It remained alive for a while but it could not eat seeds that were placed in front of it. Even though it was hungry, it would not eat.
If it was allowed to fly, it flew until it hit a barrier and fell down.