The commonwealth of cells

by H. G. F. Spurrell

Babies have to learn to interpret what they see in much the same way, and take longer about it. The child who cries for the moon is probably not so unreasonable as people think. He focuses his eyes upon the little, bright, sharply-defined disc, and it appears to him, if not actually within arm’s length, at any rate near enough to be caught with a butterfly-net. It is only after he has seen it sink behind a large tree on the distant horizon that he gathers a vague idea of its real size and remoteness.

The term ‘physical culture,’ as usually applied, is supposed only to mean the development of the muscles and viscera; really it only begins there. After the organs of nutrition have been got into a healthy state the motor organs are developed. Finally the nervous system should be trained. Mere muscle will not make even a good runner. He must practise carefully till he can take his full stride, and do so without wasting energy by any needless movements. Then he must make the action which his brain has decided is the most effective for his build the property of his spinal cord, that in a race he may use his strength economically, with his thoughts free to deal with the tactics of his opponents and the peculiarities of the course, or he will not make his supreme effort at the most advantageous moment. This is only one instance. Many men having a normal body develop organs of perception, not motion: the musician and the wine-taster, as well as the juggler and the athlete, are products of physical culture. Even the philosopher must foster the physical basis of intellect.

The education of the nervous system goes on all through life; and just as oft-repeated actions become automatic, so are habits of thought formed which are almost as regular; in fact, we might almost call them cerebral reflexes. Without constant exercise, men lose their flexibility of mind as well as of body.

But we have already passed the boundaries of our subject, and it is time for us to pull up, lest we trench further upon another science; for the study of the mind is the province, not of the physiologist, but of the psychologist.

II.

Notwithstanding the strange powers of protoplasm, and notwithstanding that these are accumulated and intensified in the body, as we saw in the last chapter, there are immovable limitations to vital activity.

This is a fact familiar to all. We can trace diminishing vitality through a series of stages, from slight fatigue right up to death itself. Sleep is perhaps one of the most interesting, though it is little understood. During sleep and the hypnotic trance, we know that the cells of the hemispheres pause in their work and chemically recruit themselves; that there is an interruption of consciousness; and that changes occur in the respiratory and circulatory, and, in fact, in most of the functions. But exactly how these states are induced we do not know. It has been suggested that during sleep less blood passes through the brain; but this is unlikely, and still less probable is it that the nerve cells draw in their processes and shut up like sea-anemones, as another daring theorist supposed. We can only draw parallels between the cells of the central nervous system and any others; all need rest.

The simplest unicellular animals, which we have mentioned so often already, spend their lives in alternate spells of activity and rest. In [the third essay] we mentioned briefly the weakening of each successive response when a muscle, in which tissue fatigue has chiefly been studied, is stimulated. Before the muscle contracted it contained a form of sugar; when it is tired the sugar is gone, and has been replaced by the products of the chemical action by which the energy was evolved. A period of rest must then follow, for the muscle to be cleansed and replenished. The case of glands, described in [Essay II.], is somewhat similar. After the gland cell has discharged its ferment, it must spend some time secreting a fresh stock before it is ready to discharge again. In fact, a cell seems to load itself up with supplies, like a locomotive with coal, and, after working till the fuel is nearly exhausted, it has to stop to take in more.

All the cells in the body rest at times; even the cells of the heart, carefully as they are nourished and incessant as their work seems, rest between each beat, and the cells of the nervous system form no exception. The brain no less than the body requires periodic rests to renew its chemical stores, and these rests have to be all the longer, as during the waking hours the brain works harder and less intermittently than any other organ. It is only because the brain is the seat of consciousness and the source of voluntary movements that these phenomena are suspended during sleep.

Death may seem at first sight a very simple affair, the breaking up of protoplasm into simpler non-living compounds; but the death of the body is anything but simple—in fact, it is not always easy to say when the body is dead. Usually, however, it is considered dead when the central nervous system has succumbed, though the muscles may continue to live for several hours.