Okay, okay, I know what you're thinking. What the heck am I doing talking about headless chickens on Science Sundays? Fear not, there is a method to my madness. Mike the Headless Chicken was a very special rooster who was born in April 1945. He was going to be killed and cooked up for a meal, but luckily (or perhaps not), he lived for 18 months after his head was cut off--read more to learn how!
According to the story, on September 10, 1945 Lloyd Olsen was going to cook Mike up and serve him as the family dinner. Knowing that his mother-in-law would enjoy the tender neck meat, he attempted to leave as much of the neck as possible on the chicken as he cut its head off. However, after the blow not only did the chicken not bleed to death, but it continued with its normal activities and was found the next day sleeping with his own head under his wing. Impressed by the chicken's will to live, Olsen fed it a mixture of milk and water with an eye dropper, along with small bits of corn. It grew from 2 pounds to 8 pounds, and was a happy healthy chicken until he died 18 months later when he choked at night.
But how could he have survived at all?
Turns out that when Olsen cut off Mike's head, he had missed the jugular vein and a blood clot had prevented Mike from bleeding to death. He had also left one ear and most of the brain stem intact--which regulates basic functions (heart rate, breathing, temperature) and most of a chicken's reflex actions. It was the mostly intact brain stem that had allowed him to live life as a regular chicken, even though the rest of his brain was gone along with his head.
The brain stem is a very primitive part of the brain. It is the most crucial, since it controls all of unconscious processes that allow us to live. The rest of the brain controls sensory perception and higher function (though, being a headless chicken and all, Mike didn't need much of that).
You'd think that, being the control system of our bodies, we would need our entire brains in order to live, but it isn't so--not in chickens, and not in humans either. In extreme cases, people with grand mal seizures that originate in one hemisphere of the brain have half of their brain removed in order to alleviate their condition. These people survive and remain almost completely functional, if not for some peculiar limitations.
Isn't the brain amazing?