I like cats since childhood. And from early years I admire their ability to jump down. During war we had a very big cat brought by my father from an expedition. We called him Fedot-cat. He was a serious animal. He caught rats and wasn't scared of dogs at all. And they in their turn felt respect to him, though like his neighbor's cats. He easily jumped on high staging and stacks of firewood in the yard. Without fear he jumped down the roof of our house. Looking at him I thought: why doesn't he hurts? At that time that height seemed considerable to me. I couldn't suppose that cats are able to jump down even higher.
I also remember one more event. At tat time I was a student and did a practical work at the biological station of MSU. A stray kitten lived there. He was kept out the houses, and not that he aspired to go there: he was wild and self-will. He didn't yield to anybody. Once I returned from the morning excursion and heard crows made noise. I tried to understand the reason of that tumult. A crow nest is on a high tree, our kitten - below it, on a thick brunch. Crows lose their temper and approach closer. The kitten cuddled up, twirls his head, and shows his teeth. But this doesn't stops the owners of nest. Here one of them attacks him and throws him from the brunch. The kitten falls down, somersaulting at first. And then he turns legs down and glides. He landed in the grass and, followed by crows, rushed right then and hided under the bush.
By that time I seriously interested in the abilities of animals to control their body in the air. Of cause birds, bats and dragonflies were beyond comparison. But cats don't have wings. Nevertheless they are able to orient their body in space in such way as to land on all four limbs and at that not to be injured much. This is possible only in the presence of perfect sense of balance that in terms of technique is called "gyroscope"; it's situated inside the interior ear, in the neighborhood of cochlea - the organ of hearing. The cat "gyroscope" is called vestibular apparatus and its construction is as follows.
As the picture shows there are two membranous structures in vestibular organ of cat termed sacks. The sacks in their turn are called utricle and sacculus. Sacks are filled with a special liquid - endolimph, and are with a singular prominence in each called spot, or macula. In each macula there're perceptive cells with filaments. Spare endings of filaments penetrate though a jelly-like semi-transparent mass that covers them. This mass is called an otolith membrane and contains microscopic crystals of calcium carbonate and calcium phosphate. Endings of vestibular nerve fibers come into approach of perceptive cells.
During moving irregularly, accelerating or slackening speed, during jolty or tossing, or alterations of position of head and body the otolith membrane shifts and presses perceptive filaments or changes their tension. This causes irritation of nerve endings.
Three membranous semicircle channels approach to utricle. They are situated in three inter-perpendicular planes - horizontal, vertical-transverse and vertical-longitudinal. Each of channels begins and terminates in utricle, but two of them are accreted with its endings and open in the sack with one aperture. Thus, semicircle channels are connected to utricle with five apertures, not six.
Endings of channels that open into utricle dilate in a form of ampoule and have a prominence inside, called crysta. Crysta carries perceptive cells with filaments and supporting cells. Perceptive cells are surrounded with endings of vestibular nerve. Filaments of perceptive cells are plunged in semi-transparent mass called cupola or roof.
Semicircle channels are filled with endolimph which, when shifted by mechanical power, deflects copula and bends filaments causing stimulation of nerve endings. An irritating factor here is acceleration and deceleration of rotator movement. Endolymph shifts along the channel, deflecting cupola and bending perceptive filaments thereby irritating nerve endings.
Information about changes in orientation of body through the vestibular nerve fibers passes into medulla, and then - partly into cerebellum and partly into vestibular nuclei of pons. One portion of fibers goes into nuclei called in honor of scientists who described them - Deuters, Schwalbe and Behterev. Though information flow from the vestibular apparatus ultimately reaches cerebral cortex that takes a final decision, it is checked and used by intermediate levels, and first of all, cerebellum.
But semicircle channels are charged not only with balance. Muscles that support neck, body and limbs are connected with vestibular apparatus activity. During high-altitude jumps-falls this is especially important. The same thing is about moving along the tree brunches. Let's watch a cat climbed on the tree. With an astonishing grace it walks along a thin brunch, slightly bent under its' weight. And here it fearlessly steps along a fence surveying close surroundings.
But, of cause, the most amazing thing have been high-altitude jumps-falls of cats. The figures that are the evidence of how far cats manage to fall down and stay alive are as follows.
The record-breaker (kitten called Sabrina) fell down from the 32nd floor, stayed alive and got only slight injuries. It's well known that cats that fall from higher floors bear this jumps easier and get less injuries than those that jump down from the windows situated lower for example sixth floor. Though real reasons of this effect are not that clear, scientist believe that it is the ratio of body weight to its' square, smaller then in humans that is important. If a cat falls from the sixth floor its' limit speed reaches 100 km/h, man falling from the same height will make twice as much. At that a cat lands on four legs, skillfully relaxed, in addition.
Falling from a big height a cat within a certain distance to a touchdown area throws its' paws out like an experienced parachutist just on reaching the maximum speed of fall. In short, in that case, we have some things to learn from cats.
Valeriy ILYICHEV, Doctor of Biology, professor
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).