The natural sciences, therefore, show among their scholars professed enemies of coffee. They are, from a medical as well as economical point of view, decidedly opposed to its use. Some have even gone so far as to declare it poisonous; a naturalist by name of Zobel proved that it contains Prussic acid, one of the deadliest poisons. Fortunately we know that this Prussic acid is rendered ineffectual by the ammoniac which coffee contains, and which is used as an antidote against Prussic acid. Be this as it may, we have reason to esteem coffee very highly. A beverage which has become such a necessity to every nation, is of great importance; and the instinct with which millions and millions of our fellow-men are drawn to its enjoyment, is the best proof that the use of coffee is not hurtful, but advantageous to man; notwithstanding the fact that in some diseases it is forbidden, and that science has not yet succeeded in showing us the real advantage of coffee as a means of food. CHAPTER IV. COFFEE AS A MEDICINE. In recent times coffee has been considered, not as an article of food, but partly as a spice and partly as a kind of medicine. Spice it is, inasmuch as it causes, like many other spices, the stomach to secrete an increased quantity of gastric juice. Digestion only takes place when the sides of the stomach secrete a liquid having the quality of digesting food. Owing to this, well-to-do people take after dinner a cup of coffee in order to promote digestion. It is because at night the power of digesting is very much enfeebled--hence the bad sleep after one has eaten something difficult to digest--and because the stomach is relaxed and inactive, that a cup of coffee in the morning refreshes and stimulates the coats of the stomach, and causes there renewed vigor and activity. It is a common observation, that more appetite is felt after coffee than before it. So much for the importance of coffee as a spice. Very justly we ascribe to coffee also a medicinal influence; we consider it a medicine for our mental activity, and for the activity of the nerves. It is well known that at night coffee dispels fatigue, and that by the use of strong coffee sleep may be banished for a long time. And more; those that are busy mentally, often feel a fresh, invigorating impulse after the enjoyment of coffee; when fatigued with work, they make it a means to recruit their strength. For a similar reason, coffee can animate conversation. When we meet elderly ladies in society, and notice them sitting quietly and talking but in monosyllables, we need not be surprised; they have had no coffee yet! But when, after a little, conversation flows with full force like a rapid stream of water, we may from this safely recognize the mighty influence of coffee; it has loosened not only the tongues, but more--the looks, the hands, nay, the whole body and the whole soul.