Gateways to the Mind

[Music] the Bell Telephone system brings you another of its series of programs on science man's effort to understand nature's laws [Music] [Applause] la [Music] The Sound Stage with its gadgets and Equipment will serve as a sort of Workshop in the telling of our science story human senses how they work and what they mean to man and to help us along we'll have the assistance of various members of the crew who work [Music] here thanks for the tour Bill quite a place this Sound Stage yeah they're ready on the Aristotle set doctor oh thanks let's go oh doc I always thought this Aristotle was a real old guy with a long beard you know real ancient well Bill although Aristotle lived about 2500 years ago he wasn't always an ancient when he was a young man like many other people of his time he was interested in trying to learn about the human senses but here he is getting a shave and surrounded as always by some of his students [Music] certainly there is nothing more distressing to the human senses than a dull razor Master continue udus what are your thoughts concerning the human senses as meat and wine are nourishment to the body the senses provide nutriment to the soul all knowledge must come through the senses all that we perceive and all of the awareness of our daily existence then we may summarize thus these senses bring us touching seeing hearing tasting smelling and all that we know of the world comes to us through these five senses so Aristotle was the first guy to figure it out huh not the first maybe but Aristotle wrote some very interesting things about the senses well worth reading today yeah but everything comes to us through our senses yes indeed bill now you think about it without the information your senses bring you you'd be like a man locked in a dark cave now in one big respect Aristotle was wrong we have many more than five senses and for another thing we don't hear with just our ears alone we don't smell just with our noses we don't taste just with our tongues hey wait a minute doc after 20 years behind this camera you're not going to tell and see with my eyes are you no in the strict sense you don't Hal your eyes like your other sense organs simply receive Impressions from the outside send them onto the brain and that gets into my department doctor good it's always interesting to see what you animators come up with well trying to draw a character that represents a sense pretty tough assignment huh you bet but we have to show how they work so we finally came up with our old friend Mercury Messenger to the gods but a kind of a a wiry electrical Mercury very quick responsive number one supplies us with a big percentage of our information reacts to the air vibrations we call sound one of the two chemical senses another chemist taste specialist reacts only to Salty Sweet Bitter and sour responds to changes in surface or or skin condition ations so there they are the familiar five but not like Messengers really more like dispatchers dispatching information through the network of the sensory nervous system let's see how touch does it okay now let's take the tip of the finger that's where the sensory endings of touch are most plentiful when the skin touches something our friend here dispatches a sort of signal to headquarters well in very simple terms that's about what happens but how that signal gets to headquarters in the brain that's the first part of our big story within our bodies is a marvelous network of nerves nerves that carry the signals and carry them to the brain carry the signals but how Doc by electricity see the nerves of this networ made up of the long thin fibers of living nerve cells nerve cells that can make their own electricity Luigi galvani experimenting with what was then known as animal electricity accidentally touched the big muscle in the leg of a frog with two pieces of metal that were in contact with each other the electrical stimulus caused the Frog's leg to jump that was almost 200 years ago the arguments that grew out of galvani's experiment led to vault's discovery of the principle of the electric battery doc don't tell me I got an electric battery somewhere inside of me no not batteries but nerve cells hundreds of millions of them each capable of making electric charges Bill turn on this machine will you this is an actual recording of the electrical impulses going from a living eye to a living brain HK heartline of the Rockefeller Institute for medical research who made this recording is studying patterns of impulses in the optic nerve fibers and how these patterns serve as information for the brain these impulses race through our sensory system whenever sense receptors trigger electrical discharges into the nerve fibers each nerve cell passes the impulse Along by discharging its electricity to fire the next cell in the chain the impulses jump along it speeds up to 100 m an hour or more these living cells are self-charging they recover and are ready to fire again in a tiny fraction of a second doc then this nerve Network can carry all the different signals from all the different senses yes that's a funny thing the senses are all different the signals are all alike yeah but then how could the brain know which sense is sending the message pH you've just asked the big question that brings us up to the brain it's the areas in the brain the specific areas where the signals end up that tell us whether we are touching seeing hearing tasting or smelling ever since johanes Mueller German physiologist of the 19th century recognized this scientists have been trying to understand understand how the brain transforms information it receives into action sensation and thought after all it's not the easiest thing in the world to look in on the actions and workings of a living brain maybe that's where the animator has an advantage he can invent one that's an interesting look here's just a few of the hundreds of sketches that we waited through trying to make our drawings agree with your facts couldn't find a place for those 12 billion nerve cells H you no we soon realized that the best we could hope to do was map a part of it into a kind of a electronic headquarters this is our latest try and it shows up pretty well on this enlarge drawing most of the nerve impulses enter here from the spinal cord uh-huh and they pass through here to this relay Center at the base of the brain yes that would be what is called the thalamus and the impulses go on upward to their destination yes their destination in the gray outer layer of the brain called the cortex we've drawn electronic tool tubes to indicate the areas where the messages come in oh here's a better view now you see if the impulses came from the eye they'd come down through here in the same way we've set up tubes for the ear nose tongue touch and all the rest and these electrical impulses come alive as pictures on what we call the master receiver and I suppose the smaller screen represents the memory section right impressions are recorded and stored there for later reference now here on the master dispatching board we transform sensory information into conscious action walking talking and so on all right let's see this electrical headquarters of yours in operation well L's in charge of the making it work department so L's the one who really has to make these drawings move huh well I do the thinking and he does the work thanks Dad well doctor we've animated a little sequence here about a character we call Joe commuter here he is undisturbed by any outside uh stimulus like that 7:15 specially he takes five mornings a week who's the little man he's new around here isn't he well he represents the thinking part of Joe's brain he checks things against memory and past experience and decides Joe's actions on the probabilities of the future Joe Joseph [Music] [Laughter] next on the agenda breakfast good morning dear and so the day begins [Music] what a beautiful day it's nice to live in the country I think I'll walk to the station well what do you know wild strawberries they used to taste wonderful when I was a kid hold it hold it right there now let's back up and break that action down into slow motion and see what happened the first thing Joe has to decide is whether these really are strawberries that's where the eye comes in H they look familiar let's [Music] check strawberry huh of course well what about the other senses not much action here strawberries aren't very noisy [Music] [Music] meanwhile touch is checking up on everything coming in contact with the [Music] skin and so headquarters is informed the berry is picked wait a minute how about checking with the lab sense of smell ahuh and that worried look is natural after all how do you describe the smell of a strawberry stimulus dispatched analyzed okay by headquarters go ahead eat it taste it another chemist gets into the ACT taste this time how is it should be [Music] sweet sour sour well a lot happened in those few moments and Lou what was it that triggered all those little sensory characters into action well the light from the strawberry carried the stimulus to the eye be buzzing stimulated the ear and the chemical reaction on the nose and tongue stimulated the sensory endings of smell and taste stimulus that's the key word stimulus is that film ready all set doctor fine let's take a look at it it's the key word because all forms of life respond to a stimulus it's one of the things that all living creatures have in common turn it on Bill just as human beings with their complicated sense organs and nervous systems respond to the stimulus of touch so do the simplest one- cell animals which can be seen only with a microscope this is an amoeba these various single cell animals have of course no specialized sensory cells or nervous systems but they lead A busy life in their microscopic world the first important groups of multi-celled animals have a simple nerve Network connecting individual sensory cells and are particularly sensitive to [Music] touch jellyfish have notches around the perimeter of their bodies in which there are sense organs sensitive to light and to food this inquisitive looking animal uses his tentacles for touch but also has an eye at the base of each of them these more complex animals have the sensory cells grouped together into sensory organs connected by a nervous system with a primitive brain in the insect world you may find many surprises the hearing organs of the grasshopper are on the side of his abdomen and he tastes food even before he eats it with small appendages outside his mouth most insects have organ for both touch and smell on their antenna in some insects sight is more important the dragonfly has unique compound eyes that practically cover his head fish can taste all over their bodies like other animals their sense organs developed according to their particular needs the chameleon can look in two directions at once because each eye works independently of the other the alligator has an extra eyelid to protect his eyes when he opens them underwater some snakes like the pit viper have a special Sense on their faces that detects the heat of warm-blooded prey at a distance among the birds of prey the faul and especially has a Keen Eye the cat whose senses are all quite welld develop is highly sensitive to the stimulus of touch on the tips of his whiskers in each in the pattern of each animal's sensory development is reflected in the development of its unique brain structure compared to those of many animals man's senses are much less acute he can't see like a falcon smell everything a dog smells but man lives by his wits as well as his senses man and only man possesses a brain that gives him the capacity of imagination and thought far beyond the limited mental activity needed for daily survival an only man has developed a singular ability to speak to reason and to plan far into the future [Music] George I know that this is your office but what exactly happens here my job is to control the strength of the electrical currents coming from the microphones and bring them into balance on this console it's called mixing and then it's recorded on film not anymore Magnetic Tape now in other words these sounds are first converted into electrical impulses and then they're balanced and Amplified in this console and then record it that's correct that's a lot like the ear works vibrations electricity sound so it is but George's ear is a much more complicated instrument than the equipment he operates how does the inside of the human hearing apparatus look to an animator Jean well I'll tell you Doctor let's find out by following the sound of Chopsticks right into George's [Music] ear the outer ear is shaped somewhat like a funnel ending at the ear drum the surface of the eardrum is pushed back and forth by the vibrations of the sound wave the movement of the e drum sets the oses in action three little bones commonly known as the hammer Anvil and stup this film shows the human eardrum which is only about a qu of an inch across these are the ticles that work within the human ear the tiny stup works with a rocking motion creating pressure on the fluid of the inner ear the ccka driving back and forth this little lever mechanism increases the pressure about 10 times and now we discover what really happens to Chopsticks here's a simplified view of the ccka it's lined with a thin Bassel membrane which contains 24,000 hairlike cells in this illustration they somewhat resembl the keyboard of a piano the sound waves now transformed into fluid pressure waves disturb the hairlike cells along the Bassel keyboard according to the pit of the notes each pitch vibrates a particular group of tiny hair cells triggering electrical impulses that proceed along the auditory nerve and form a brain pattern which to us means [Music] music now those nerve impulses we heard a while ago they're the same for uh well seeing or hearing well to answer your question Bill come and help me with you here again is Dr harlin's recording of optic nerve impulses Dr Lloyd bider Florida State University has made these recordings of impulses originating in the taste buds recordings have also been made for smell for impulses from the AL Factory nerve they're all the same yes the impulses for all the senses are the same there's another interesting thing a little further on this role here as the stimulus from outside increases the number of impulses goes up accordingly these things were first demonstrated in the 1920s by Ed Adrien of the University of Cambridge it's the same with all of our senses taste for instance this time the chemicals of food or drink excite the hairlike cells of the taste buds which line the crevices of our tongues the remarkable thing is that taste is not just one sense it's actually Four sweet salt sour and bitter seems to me I taste more different ways than just four that's because when you're tasting things you're also smelling things the range of smell seems to be boundless seem to be about as many different smells as there are things to smell and of course taste plus smell equals flavor Jean come on we have to go over the westries sure you know a fell told me that if you hold your your nose you can't tell whether youve got a little piece of apple or onion on your tongue yeah how about that that's right when we taste something the chances are we also smell it hey Doc this pop tastes cold am I smelling that oh yes that's another thing in our mouths we have temperature senses which react to ice cream hot coffee hot and cold things certainly we find that the sense of smell is most useful to man perhaps primitive man like the animals made much greater use of it for most animals smell is still the most trustworthy scense turn on the machine will you the delicate thawn uses his sensitive nose as well as his ears to warn of approaching danger many stories are told about the moth's extraordinary sense of smell with receptors located on its most remarkable antenna ants too have receptors for smell on their antenna now we know about the rabbit big ears always cocked and a busy nose always alert and speaking of a busy [Music] nose bill in the case of the dog do you know what he was smelling a bone molecules you mean to say we smell molecules whatever we smell is in the form of tiny molecules that being volatile take off into the air we smell them as odors Aromas for example they bring us the first sweet scent of new spring blossoms rich and long remembered experiences come to us through the air as Tiny molecules and wafted free on the clear morning Breeze they can smell mighty good we help the molecules get to the right place by sniffing they wind up in a chemical laboratory for that's what the upper chamber of the nose actually is when the molecules reach this chamber they chemically stimulate the millions of cell filaments on all Factory patch and from here as in the case of the other senses messages races electrical impulses to the brain where we experience the sense of smell all [Music]