According to Dr. Hollingworth's[285] deductions, caffein is the only known stimulant that quickens the functions of the human body without a subsequent period of depression. His explanation for this behavior is that "caffein acts as a lubricator for the nervous system, having an actual physical action whereby the nerves are enabled to do their work more easily. Other stimulants act on the nerves themselves, causing a waste of energy, and consequently, according to nature's law, a period of depression follows, and the whole process tends to injure the human machine." In not a single instance during his experiments at Columbia University did depression follow the use of caffein.

Of course, caffein, like any other alkaloid, if used to excess will prove harmful, due to the over-stimulation induced by it. However, taken in moderate quantities, as in coffee and tea by normal persons, the conclusions of Hirsch[286] may be taken as correct, namely: caffein is a mild stimulant, without direct effect on the muscles, the effect resulting from its own destruction and being temporary and transitory; it is not a depressant either initially or eventually; and is not habit-forming but a true stimulant, as distinguished from sedatives and habit-forming drugs.

Caffein and Mental and Motor Efficiency

The literature on the influence of caffein on fatigue has been summarized, and the older experiments clearly pointed out, by Rivers[287]. A summary of the most important researches which have had as their object the determination of the influence of caffein on mental and motor processes has been made by Hollingworth[288], from whose monograph much of the following material has been taken.

Increase in the force of muscular contractions was demonstrated in 1892 by De Sarlo and Barnardini[289] for caffein and by Kraepelin for tea. These investigators used the dynamometer as a measure of the force of contraction; however, most of the subsequent work on motor processes has been by the ergographic method. Ugolino Mosso[290], Koch[291]. Rossi[292], Sobieranski[293], Hoch and Kraepelin,[294] Destrée,[295] Benedicenti,[296] Schumberg,[297] Hellsten,[298] and Joteyko,[299] have all observed a stimulating effect of caffein on ergographic performance. Only one investigation of those reported by Rivers failed to find an appreciable effect, that of Oseretzkowsky and Kraepelin,[300] while Feré[301] affirms that the effect is only an acceleration of fatigue.

In spite of the general agreement as to the presence of stimulation there is some dissension regarding whether only the height of the contractions or their number or both are affected. As might be expected from the great diversity of methods employed, the quantitative results also have varied considerably. Carefully controlled experiments by Rivers and Webber[302] "confirm in general the conclusion reached by all previous workers that caffein stimulates the capacity for muscular work; and it is clear that this increase is not due to the various psychical factors of interest, sensory stimulation, and suggestion, which the experiments were especially designed to exclude. The greatest increase ... falls, however, far short of that described by some previous workers, such as Mosso; and it is probable that part of the effect described by these workers was due to the factors in question."

Investigations of mental processes under the influence of caffein have been much less frequent, most notable among which are those of Dietl and Vintschgau,[303] Dehio,[304] Kraepelin and Hoch,[305] Ach,[306] Langfeld,[307] and Rivers.[308] Kraepelin[309] observes: "We know that tea and coffee increase our mental efficiency in a definite way, and we use these as a means of overcoming mental fatigue ... In the morning these drinks remove the last traces of sleepiness and in the evening when we still have intellectual tasks to dispose of they aid in keeping us awake." Their use induces a greater briskness and clearness of thought, after which secondary fatigue is either entirely absent or is very slight.

Tendency toward habituation of the pyschic functions to caffein has been studied by Wedemeyer[310], who found that in the regular administration of it in the course of four to five weeks there is a measurable weakening of its action on psychic processes.

Rivers[311], who seems to have been the first to appreciate fully the genuine and practical importance of thoroughly controlling the psychological factors that are likely to play a rôle in such experiments, concludes that "caffein increases the capacity for both muscular and mental work, this stimulating action persisting for a considerable time after the substance has been taken without there being any evidence, with moderate doses, of reaction leading to diminished capacity for work, the substance thus really diminishing and not merely obscuring the effects of fatigue."

Subsequent to these investigations was that of Hollingworth[312] which is at once the most comprehensive, carefully conducted, and scientifically accurate one yet performed. He employed an ample number of subjects in his experimentation; and both his subjects, and the assistants who recorded the observations, were in no wise cognizant of the character or quantity of the dose of caffein administered, the other experimental conditions being similarly rigorous and extensive.

The purpose of his study was to determine both qualitatively and quantitatively the effect of caffein on a wide range of mental and motor processes, by studying the performance of a considerable number of individuals for a long period of time, under controlled conditions; to study the way in which this influence is modified by such factors as the age, sex, weight, idiosyncrasy, and previous caffein habits of the subjects, and the degree to which it depends on the amount of the dose and the time and conditions of its administration; and to investigate the influence of caffein on the general health, quality and amount of sleep, and food habits of the individual tested.

To obtain this information the chief tests employed were the steadiness, tapping, coordination, typewriting, color-naming, calculations, opposites, cancellation, and discrimination tests, the familiar size-weight illusion, quality and amount of sleep, and general health and feeling of well-being. A brief review of the results of these tests is given in the tabular summary.

From these Hollingworth concluded that caffein influenced all the tests in a given group in much the same way. The effect on motor processes comes quickly and is transient, while the effect on higher mental processes comes more slowly and is more persistent. Whether this result is due to quicker reaction on the part of motor-nerve centers, or whether it is due to a direct peripheral effect on the muscle tissue is uncertain, but the indications are that caffein has a direct action on the muscle tissue, and that this effect is fairly rapid in appearance. The two principal factors which seem to modify the degree of caffein influence are body weight and presence of food in the stomach at the time of ingestion of the caffein. In practically all of the tests the magnitude of the caffein influence varied inversely with the body weight, and was most marked when taken on an empty stomach or without food substance. This variance in action was also true for both the quality and amount of sleep, and seemed to be accentuated when taken on successive days; but it did not appear to depend on the age, sex, or previous caffein habits of the individual. Those who had given up the use of caffein-containing beverages during the experiment did not report any craving for the drinks as such, but several expressed a feeling of annoyance at not having some sort of a warm drink for breakfast.

It is interesting to note that he also found a complete absence of any trace of secondary depression or of any sort of secondary reaction consequent upon the stimulation which was so strikingly present in many of the tests. The production of an increased capacity for work was clearly demonstrated, the same being a genuine drug effect, and not merely the effect of excitement, interest, sensory stimulation, expectation, or suggestion. However, this study does not show whether this increased capacity comes from a new supply of energy introduced or rendered available by the drug action, or whether energy already available comes to be employed more effectively, or whether fatigue sensations are weakened and the individual's standard of performance thereby raised. But they do show that from a standpoint of mental and productive physical efficiency "the widespread consumption of caffeinic beverages, even under circumstances in which and by individuals for whom the use of other drugs is stringently prohibited or decried, is justified."

Conclusion

Brief summarization of the information available on the pharmacology of coffee indicates that it should be used in moderation, particularly by children, the permissible quantity varying with the individual and ascertainable only through personal observation. Used in moderation, it will prove a valuable stimulant increasing personal efficiency in mental and physical labor. Its action in the alimentary régime is that of an adjuvant food, aiding digestion, favoring increased flow of the digestive juices, promoting intestinal peristalsis, and not tanning any portion of the digestive organs. It reacts on the kidneys as a diuretic, and increases the excretion of uric acid, which, however, is not to be taken as evidence that it is harmful in gout. Coffee has been indicated as a specific for various diseases, its functions therein being the raising and sustaining of low vitalities. Its effect upon longevity is virtually nil. A small proportion of humans who are very nervous may find coffee undesirable; but sensible consumption of coffee by the average, normal, non-neurasthenic person will not prove harmful but beneficial.

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Chapter XIX

THE COMMERCIAL COFFEES OF THE WORLD

A study of the geographical distribution of the coffee tree shows that it is grown in well-defined tropical limits. The coffee belt of the world lies between the tropic of cancer and the tropic of capricorn. The principal coffee consuming countries are nearly all to be found in the north temperate zone, between the tropic of cancer and the arctic circle.

The leading commercial coffees of the world are listed in the accompanying commercial coffee chart, which shows at a glance their general trade character. The cultural methods of the producing countries are discussed in chapter XX; statistics in chapter XXII; and the trade characteristics, in detail, in chapter XXIV, which considers also countries and coffees not so important in a commercial sense. Mexico is the principal producing country in the northern part of the western continent, and Brazil in the southern part. In Africa, the eastern coast furnishes the greater part of the supply; while in Asia, the Netherlands Indies, British India, and Arabia lead.

Within the last two decades there has been an expansion of the production areas in South America, Africa, and in southeastern Asia; and a contraction in British India and the Netherlands Indies.

The Shifting Coffee Currents of the World

Seldom does the coffee drinker realize how the ends of the earth are drawn upon to bring the perfected beverage to his lips. The trail that ends in his breakfast cup, if followed back, would be found to go a devious and winding way, soon splitting up into half-a-dozen or more straggling branches that would lead to as many widely scattered regions. If he could mount to a point where he could enjoy a bird's-eye view of these and a hundred kindred trails, he would find an intricate criss-cross of streamlets and rivers of coffee forming a tangled pattern over the tropics and reaching out north and south to all civilized countries. This would be a picture of the coffee trade of the world.

It would be a motion picture, with the rivulets swelling larger at certain seasons, but seldom drying up entirely at any time. In the main the streamlets and rivers keep pretty much the same direction and volume one year after another, but then there is also a quiet shifting of these currents. Some grow larger, and others diminish gradually until they fade out entirely. In one of the regions from which they take their source a tree disease may cause a decline; in another, a hurricane may lay the industry low at one quick stroke; and in still another, a rival crop may drain away the life-blood of capital. But for the most part, when times are normal, the shift is gradual; for international trade is conservative, and likes to run where it finds a well-worn channel.

In recent times, of course, the big disturbing element in the coffee trade was the World War. Whole countries were cut out of the market, shipping was drained away from every sea lane, stocks were piled high in exporting ports, prices were fixed, imports were sharply restricted, and the whole business of coffee trading was thrown out of joint. To what extent has the world returned to normal in this trade? Were the stoppages in trade merely temporary suspensions, or are they to prove permanent? How are the old, long-worn channels filling up again, now that the dams have been taken away?

We are now far enough removed from the war to begin to answer these questions. We find our answer in the export figures of the chief producing countries, which for the most part are now available in detail for one or two post-war years. These figures are given in the tables below; and for comparison, there are also given figures showing the distribution of exports in 1913 and in an earlier year near the beginning of the century. These figures, of course, do not necessarily give an accurate index to normal trade; as in any given year some abnormal happening, such as an exceptionally large crop or a revolution, may affect exports drastically as compared with years before and after. But normally the proportions of a country's exports going to its various customers are fairly constant one year after another, and can be taken for any given year as showing approximately the coffee currents of that period.

The figures following are for the calendar year unless the fiscal year is indicated. Where figures could not be obtained from the original statistical publications, they have been supplied as far as possible from consular reports.

Brazil. The war naturally increased the dependence of Brazil on its chief customer, and the proportion of the total crop coming to this country since the war has continued to be large. Shipments to United States ports in 1920 represented about fifty-four percent of the total exports. Figures for that year indicate also that France and Belgium were working back to their normal trade; but that Spain, Great Britain, and the Netherlands were taking much less coffee than in the year just before the war. Germany was buying strongly again, her purchases of 72,000,000 pounds being about half as much as in 1913. Shipments to Italy were four times as heavy as in 1913. The natural return to normal was much interfered with by speculation and valorization. Brazil seems to have come through the cataclysmic period of the war in better style than might have been expected.

The 1900 figures are for the ports of Rio, Santos, Bahia, and Victoria.

"Other countries" in 1913 included Argentina, 32,941,182 pounds; Sweden, 28,045,737 pounds; Cape Colony, 15,930,731 pounds; Denmark, 6,252,931 pounds. In 1920 they included Argentina, 37,736,498 pounds; Sweden, 51,026,591 pounds; Denmark, 18,764,483 pounds; Cape Colony, 26,936,653 pounds.

Venezuela. Venezuela's coffee trade was deeply affected by the war; both because the Germans were prominent in the industry, and because the regular shipping service to Europe was discontinued. Large amounts of coffee were piled up at the ports and elsewhere; and when the restrictions were swept away in 1919, an abnormal exportation resulted. Although Germany had been one of the chief buyers before the war, Venezuela was by no means dependent on the German market. In fact, her combined shipments to France and the United States, just before the war, were three times as great as her exports to Germany. These two countries took two-thirds of her total exports in 1920. Spain and the Netherlands were also prominent buyers.

Colombia. Colombian statistics of foreign trade are issued very irregularly, and no figures are available to afford comparison between pre-war and post-war trade. The figures below, however, will show the comparative amounts of coffee going to the chief buying countries at different periods. From these it will be seen that the countries mainly interested in the trade in Colombian coffee are those prominent in the trade in other tropical American sections. England, France, Germany, and the United States took the great bulk of the exports. A consular report written after the outbreak of the war says:

"Other countries" in 1916 included Italy, 1,135,137 pounds; Venezuela, 20,564,321 pounds; Dutch West Indies, 400,132 pounds.

Central America. The three largest producing countries of Central America, Guatemala, Salvador, and Costa Rica, were all closely linked to Germany by the coffee trade before the war. German capital was heavily invested in coffee plantations; German houses had branches in the principal cities; and German ships regularly served the chief ports. Accordingly, when the blockade became effective, these countries were placed in a difficult position. But fortunately for them, a special effort had been made shortly before by Pacific-coast interests in the United States to divert a part of the coffee trade to San Francisco[313] The market to the east being shut off, these countries turned naturally to the north. This trade with the United States has apparently been firmly established, and there has not yet been much of a return to German ports.

Guatemala. Of the three countries named, Guatemala was the most heavily involved in German trade. In 1913 she sent to Germany 53,000,000 pounds of coffee, a fifth more than in 1900. Her shipments of more than 10,000,000 pounds to the United Kingdom were about the same as at the beginning of the century. The war turned both these currents into United States ports, and they continued to flow in that direction through 1920. The figures follow:

"Other countries" in 1913 included Austria-Hungary, 4,205,400 pounds; Netherlands, 407,900 pounds. In 1920, they included Netherlands, 10,355,625 pounds; Sweden, 422,421 pounds; Norway, 57,408 pounds; Spain, 97,519 pounds; France, 27,956 pounds.

Salvador. Salvador is one of the countries in which the publication of foreign-trade statistics has been irregular in the past, and none is available to show the full trade in coffee at the beginning of the century. A consular report gives figures for the first half of 1900. The most recent statistics show that the United States still holds much of the trade gained during the war, although Salvador is sending to Scandinavian countries many millions of pounds of her coffee that came to the United States in war-time.

"Other countries" in 1913 included Norway, 2,070,220 pounds; Sweden, 2,238,332 pounds; Netherlands, 738,694 pounds; Chile, 609,441 pounds; Russia, 95,625 pounds; Denmark, 140,665 pounds. In 1920, they included Norway, 10,726,375 pounds; Chile, 1,772,346 pounds; Netherlands, 1,071,614 pounds; Sweden, 9,635,947 pounds; Denmark, 1,061,772 pounds.

Costa Rica. English, French, and German capital was heavily invested in Costa Rica before the war, and all three nations were interested in the coffee trade. For many years England had maintained the lead as a coffee customer, and shipments continued in large volume after the war. The following figures are for the crop year ending September 30:

In 1900 total shipments were 35,496,055 pounds, of which 20,587,712 pounds went to Great Britain; 8,874,014 pounds to the United States; and 3,904,566 pounds to Germany.

"Other countries" in 1903 included Spain, 49,189 pounds; Italy, 4,104 pounds. In 1921, they included Netherlands, 837,496 pounds; Spain, 308,308 pounds; Chile, 9,259 pounds.

Mexico. Mexico has naturally sent most of her coffee across the border into the United States, and she continued to do so during and after the war. But she had worked up a very important trade with Europe, chiefly with Germany; and German capital, and German planters and merchants were prominent in the industry. France and England also were interested in the trade, and purchased annually several million pounds. During the war, as shown by the exports in its final year, this trade almost entirely ceased, and the United States and Spain remained as the only consumers of Mexican coffee. Details of the after-war trade are not yet available in published statistics. In the following table, 1900 and 1918 are calendar years, and 1913 is a fiscal year.