The Living CellAuthor(s): Robert ChambersSource: The Scientific Monthly, Vol. 39, No. 3 (Sep., 1934), pp. 269-270Published by: American Association for the Advancement of ScienceStable URL: http://www.jstor.org/stable/15718 .

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SCIENCE SERVICE RADIO TALKS 269

THE LIVING CELL By Dr. ROBERT CHAMBERS

PMROFSOR OF BIOLOGY, WASHINGTON SQUARB COLLEGE, NEW YORK UNIvERSITY

THE invention of the compound mi- croscope in the seventeenth oentury led to the discovery that all living organ- isms, both plant and animal, from the largest to the smallest, are composed of minute bodies called cells. These cells are such highly organized and self- sufficient units that millions of organ- isms consist of just one cell, for instance, all bacteria.

There are two good reasons why we are interested in living cells; one is our natural curiosity regarding these minute structures which embody the mystery of life and, second, the realization that in- vestigations! concerning cells bring us to the very root of the problem as to how the organs of our bodlies function. It is the knowledge of this upon which medi- cal science depends.

Cells have been a favorite object of study for a long time, but only within comparatively recent years has it been possible to subject them to experimental analysis. One of the difficulties is their small size. If we were to take average sized cells and spread them over an area of 1 square inch we would need 400 to 500 million cells to cover the space. An- other difficulty is getting at them with- out the risk of injuring them. The great majority of the cells are bound together firmly to constitute the organs of our bodies. Others, which are among the smallest of cells, lie in the blood and body fluids where they are free to move about.

One of the most promising methods devised within the last twenty years for examining living cells depends upon the discovery that tiny fragments cut from living tissues will survive in a drop of blood outside the body. The oells in the fragment spread out and, continue to grow and multiply under conditions where they can be clearly observed

through a microscope. Another useful method has been made possible by the in- vention of a mechanical contrivance which enables the experimenter to use exceedingly fine glass needles for ma- nipulating individual cells in the highly magnified field of the microscope. In short, the past fifteen years have been marked by developments which enable us to work on the problem in a much more direct manner than had been pos- sible before.

At present what do we know about the cell? We know a great deal of what it is capable of doing, but we are woefully ignorant of how it does it. This is be- cause our knowledge of its constitution is still in its veriest infancy, and even our speculations regarding it are far from satisfactory.

It has been shown experimentally that the cell is a fluidi body, marked off from its surroundings by a well-defined bound- ary or membrane. If our bodies were composed of nothing more than these cells we would be only flabby lumps of jelly. However, many of the cells de- posit about them solid materials which form our bony skeleton and, in plants, the woody parts.

The fluid of the cell is in constant mo- tion, although some parts are denser than others. Such differences in density suggest some kind of an internal organi- zation. Within this fluid we find an oval or round body which is invariably pres- ent. It is called the nucleus of the cell.

The membrane which encloses the fluid cell has such surprising properties that some investigators regard it as being that part of the cell which is chiefly responsible for the processes which make life possible. It has the faculty of selecting certain substances to pass into the cell and it rejects others. This membrane is not a permanent fix-

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270 THE SCIENTIFIC MONTHLY

ture but is constantly being broken down and as constantly being repaired. The properties of the membrane are so in- triguing that we have to-day a school of so-called, membrane physiologists who are experimenting in the laboratory with all sorts of membranes and films in the search of a material which will, in some measure, duplicate the properties of the living cell membrane. On the basis of this idea one of the prime functions of the materials within the cell seems to be to keep its membrane intact and in the proper working order.

The condition of this membrane may be illustrated by a crude analogy of a country at war with a thin line of de- fending troops surrounding it. As long as the line is intact all is well. The personnel of the line is ever chang- ing through individual replacements. Wherever the line breaks reinforcements are rushed from the interior to fill the gap. From the air the interior of the country appears to be in turmoil with troops and lorries traveling in all direc- tions. Evidence of orderly arrangement is most apparent along the thin extended line surrounding the whole. Such is the cell membrane. The life of the cell and indeed life in general is a continual ad- justment of internal to external condi- tions. This means continual work with a constant expendiutre of energy, which is obtained by the cell through nourish- ment.

How long do cells live? To answer this question we must first realize that all cells can divide into two young daughter cells. This process of cell di- vision is periodic and, in the interval between successive divisions, the two daughter cells grow to the size of the mother cell. In young organisms the cells multiply rapidly from hour to hour. As the organism ages the rate slows down until, when maturity is reached, many cells may carry on for years with- out appreciable change. However, if an injury should occur the cells can again divide and grow until they have replaced

the mutilated tissue. This indicates that the potentialities for continued growth are still present, even in old organisms. Under normal conditions these growth potentialities are held in check. Other- wise, there would be nothing to stop the cells from converting us into continually growing and monstrous giants !

The latent ability of cells to grow without control flares into activity in the dread disease of civilization, cancer. The cells which are affected by this dis- ease lose their subordination to the gen- eral economy of the body. They con- tinue to multiply and grow to form the insidious tumors which destroy the body in which they grow.

Cancer differs from the usual human afflictions in being a peculiar state of the living cell. In other diseases our resis- tance is lowered because our cells weaken and we succumb because our cells die. In cancer, on the other hand, the in- volved cells are healthy and vigorous, but they are so altered as to have lost their original functions. They persist and grow as living cells but with rela- tionships which are chaotic and vicious.

It is an interesting fact that several of the activities characteristic of the living cell have been successfully imitated with lifeless chemical compounds. This is nothing new. For many years investi- gators have prepared mixtures of vari- ous substances which are amazingly lifelike. They simulate cells in the way they move, subdivide and even grow in size. Some of these mixtures even take up oxygen and give off carbon dioxide, thus bre-athing superficially in the same way that cells do.

One of the properties of all living cells which is especially evident in cancer cells and which still baffles imitation is the periodic rejuvenation and develop- ment of fresh vigor eaeh time the cells divide. The pronounced manifestation of this property in cancer cells suggests that the essential problem of cancer and of cellular physiology are one and the same.

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