So much is to be inferred from the stimulant action of tobacco upon the medulla. Of all this complicated benefit, the brain receives perhaps the largest share. The brain receives one-fifth, or according to some authorities one-third, of all the blood that is pumped from the heart. More than any other organ it demands for its due nutrition a prompt supply of arterial blood; and more than any other organ it partakes of the advantages resulting from vigorous circulation.
The stimulant action of tobacco upon the spinal cord and the cerebral hemispheres is less conspicuous. Yet even here its familiar influence in stilling nervous tremour and allaying nocturnal wakefulness is good testimony to its essentially beneficent character. Wakefulness and tremour are alike symptoms of diminished vitality; and the agent which removes them is not to be called, as Mr. Parton in his mediæval language calls it, "hostile to the vital principle."
So much for the net results of the stimulant action of tobacco. So far we have travelled on firm ground, and we have not found much to countenance Mr. Parton's view of the subject. But now some curious inquirer may ask, what is this stimulant action? What is the physiological expression for it, reduced to its lowest terms? Here we must keep still, or else venture upon ground that is very unfamiliar and somewhat hypothetical. There is no help for it; for we cannot yet give the physiological expression for unstimulated nervous action, reduced to its lowest terms. We know what kind of work nerves perform, but how they perform it we can as yet only guess. Nor, as far as the practical bearings of our subject are concerned, does it matter whether this abstruse point be settled or not. Still, even upon this dark subject recent research has thrown some gleams of light. A nerve-centre is a place where force is liberated by the lapse of the chemically-unstable nerve-molecules into a state of relative stability.[22] To raise them to their previous unstable state, thereby enabling them to fall again and liberate more force, is the function of food. Now our own hypothesis is, that tobacco and other narcotic stimulants enable force to be liberated by the isomeric transformation of the highly complex nerve-molecules, which retain in the process their state of relative instability, and are thus left competent to send forth a second discharge of force without the aid of food.
In support of this hypothesis we have the well-known fact that tobacco, like tea, coffee, alcohol and coca, universally retards organic waste. These substances effect this result in all the tissues, and more especially may they be expected to accomplish it in nervous tissue, where their action is so conspicuously manifest.
Thus is explained the familiar action of narcotic-stimulants in relieving weariness. Weariness, in its origin, is either muscular or nervous. It implies a diminution—owing to failing nutrition—of the total amount of contractile or of nervous force in the organism; and it shows that the weary person must either go to sleep or eat something. Now every one knows how a cup of tea, a glass of wine, or a cigar, dispels weariness. Of the three agents, tobacco is perhaps the most efficacious, and it can produce its effect in only one way—namely, by economizing nervous force, and arresting the disintegration of tissue.
Thus also is explained the marvellous food-action of these substances. Tea and coffee enable a man to live on less beefsteak. The Peruvian mountaineer, chewing his coca-leaf, accomplishes incredibly long tramps without stopping to eat. And every hardy soldier, in spite of Mr. Parton, has that within him which tells him that he can better endure severe marches and wearisome picket-service if he now and then lights his pipe. The personal experience of any one man is, we are aware, not always conclusive; but our own, so far as it goes, bears out the general conclusion. It was when we were engaged in severe daily mental labour, that we first conceived the idea of employing tobacco as a means of husbanding our resources. Narcosis being steadily avoided, the experiment was completely, even unexpectedly, successful. Not only was the daily fatigue sensibly diminished, but the recurrent periods of headache, gloom, and nervous depression were absolutely and finally done away with. That this result was due to improved nutrition was shown by the fact that, during the first three months after the habit of smoking was adopted, the average weight of the body was increased by twenty-four pounds—an increase which has been permanent. No other dietetic or hygienic change was made at the time, by which the direct effects of the tobacco might have been complicated and obscured.
The statement that smoking increases the average weight of the body[23] is not, however, universally true. We have here an excellent illustration of the impracticability of laying down sweeping rules in physiology. Many persons find their weight notably diminished by the use of tobacco; and we frequently hear it said that smoking will not do for thin people, although for those who are fleshy it may not be injurious. In this there is a very natural but very gross confusion of ideas, which a little reflection upon the subject will readily clear up. It is true that moderate smoking sometimes increases and sometimes diminishes the weight; and it is no less true that in each case the result is the index of heightened nutrition! This seems, of course, paradoxical. But physiology, quite as much as astronomy, is a science which is constantly obliging us to reconsider and rectify our crude off-hand conceptions.
It is by no means true that increase of the tissues in bulk and density is always a sign of improved health. We are accustomed to congratulate each other upon looking plump and rosy. But too much rosiness may be a symptom of ill-health; and, similarly with plumpness, there is a point beyond which obesity is a mere weariness to the spirit. Nor does a person need to become as rotund as Wouter Van Twiller in order to reach and pass this point. Many persons, who are not actually corpulent, would lose weight if their nutrition could be improved. And the explanation is quite simple.
Normal nutrition is not merely the repair of tissue: it is the repair of all the tissues in the body in due proportion. This is a very essential qualification. Fibrous and areolar tissue, muscle, nerve, and fat are daily and hourly wasting in various degrees; and the repair, whether great or small, must be nicely proportioned to the waste in each tissue. If a pound is added to the weight of the body, it makes all the difference in the world whether one ounce is muscle, another ounce nerve, a third ounce fat, and so on, or whether the whole pound is fat. When one tissue gets more than its fair share, the chances are that all the others must go a-begging. The co-ordinating, controlling power of the organism over its several parts is diminished,—which is the same as saying that nutrition is impaired. Evidence of this soon appears in the circumstance that the deposit of adipose tissue is no longer confined to the proper places. Fat begins to accumulate all over the body, in localities where little or no fat is wanted, and notably about the stomach and diaphragm, causing laborious movement of the thorax and wheezing respiration. When a man gets into this state, it is a sign that the ratio between the waste and the repair of his tissues has become seriously dislocated. You can relieve him of his fat only by improving his nutrition. The German who drinks his forty glasses of lager bier per diem is said to be bloated; and we have heard it gravely surmised that the ale, getting into his system, swells him up—as if the human body were a sort of bladder or balloon! The explanation is not quite so simple. But it is easy to see how this immense quantity of liquid, continually loading the stomach and intestines, and entailing extra labour upon all the excreting organs, should so damage the assimilative powers as to occasion an excessive deposit of coarse fat and of flabby, imperfectly-elaborated connective tissue, over the entire surface of the body. And the state of chronic, though mild, narcosis in which the guzzler keeps himself, by still further injuring his reparative powers, contributes to the general result.
There are consequently four ways in which tobacco may exhibit its effects upon the nutrition of the body.