CHEMISTRY OF ORGANISMS.
An organism is a structure endowed with life, and acting by means of organs. Organic beings are of two kinds, vegetable and animal. Ordinarily there is little difficulty in discriminating between them, but there is a border line along which the two great kingdoms meet, which is as shadowy and uncertain as that uniting, in distant view, the ocean and the sky. It is usual to say that animals move their parts, and that plants do not. The former have locomotion, the latter are stationary. Animals have nerves and receive their food in cavities; plants do not. But the most important distinction of all is that the vegetable world draws its support from the mineral world, while the animal lives upon the vegetable.
SHOWING THE FAT GLOBULES IN MILK.
Both animals and plants begin their existence with a single cell. Growth consists in the enlargement and multiplication of cells. Here the physiologist terminates his investigations, and the chemist begins.
His first step, however, results in the destruction of the organism. Of him it is emphatically true, “He murders to dissect.” The moment that chemistry seeks to determine the elementary character of an organic substance, that substance ceases to have an organic form. In a sense, therefore, there is no such thing as organic chemistry. It is a convenient term, however, for the study of the chemistry of substances formed by life.
Until recently it has been supposed that the chemist could destroy organic substances, but that he could not create them. This idea is no longer held. A great number of the compounds formed by plants and animals have been produced in the chemist’s laboratory, without the aid of vital force.
While it is undoubtedly true that many of the compounds found in plants and animals are not necessarily related to organisms, there are usually some plain facts which differentiate organic compounds from inorganic. Among these may be named the following: Organic substances are usually composed of but few elements; oxygen, nitrogen, hydrogen and carbon constituting almost all their material. Ten other elements are very sparingly distributed in them.
Sixty-six elements enter into the formation of inorganic matter.
The atomic structure of the former is very complex; that of the latter is simple. For example: A molecule of the white of egg contains 222 atoms, while a molecule of salt has but two. Again, the compounds of organic existences are innumerable. Inorganic compounds are comparatively few. The former are unstable, on account of the presence of nitrogen, while the latter are fixed and quite permanent. The former are also distinguished for the many examples of isomerism they furnish. Isomeric compounds are those formed of the same elements in the same proportions. Thus, camphene, the oils of bergamot, juniper, birch, black pepper, lemon, cloves, turpentine, ginger, cubebs, orange, and many others are isomeric, each one being composed of ten atoms of carbon and sixteen of hydrogen. The difference in these volatile oils is supposed to be due to a variation of the arrangement of the atoms composing them.
Let us now briefly consider the
FOOD OF PLANTS.
This is obtained from the air and earth. The former supplies carbonic acid, and water in the form of vapor, through the stomata of the leaves; these are little mouths or breathing pores, chiefly situated on the under side of the leaf. They vary in number from one thousand to one hundred and seventy thousand to the square inch. An apple-tree leaf of average size has one hundred thousand pores. The old elm at Cambridge, under which Washington stood while reviewing the Continental army, has been estimated to produce a crop of seven million leaves, thus exposing a surface of five acres, and therefore furnishing billions of stomata. If the amount of carbonic acid gas in the air were much increased, all higher forms of animal life would perish. If it were materially lessened, vegetation would soon wither and die, involving the death of all animals, from lack of food. Plants derive the element carbon from this gas.
A PLANT STARTING IN LIFE.
According to Chevandier, an acre of beech forest annually absorbs three and one half tons of carbonic acid gas, and from this eliminates about one ton of carbon.
Most of the oxygen and hydrogen of plants is probably obtained from the water absorbed by leaves and roots. Recent experiments indicate that plants may sometimes absorb oxygen directly from the air. This is especially true in the case of buds, as may be shown by the following experiment:
Cut twigs of willow, oak or apple just before the buds are to unfold, and place the ends in a little holder containing a small amount of water, and set this in a saucer; partially fill the saucer with quicksilver; over the twigs invert a glass fruit jar filled with oxygen, so that its mouth will be sealed by the quicksilver. The buds will unfold, and some of the oxygen disappear, but if the jar be filled with hydrogen or nitrogen the buds will decay. De Saussure,[1] by a somewhat similar experiment, proved that oxygen is absorbed by the roots of plants.
SECTION OF AN EXOGENOUS STEM.
Both gases and moisture are taken up and distributed through the cells by osmose.[2] This may easily be shown; cut off the end of a carrot and scoop out the central portion of the remainder, and place in the cavity dry sugar; this will soon be converted into a syrup, and the sides of the carrot will have perceptibly shrunk, from the passage of moisture out of the cells to the sugar.
The mineral constituents of plants are all taken up by the roots in the form of solution, water being the great carrier by which plants are supplied.
The following substances are invariably present in all agricultural plants, and in many others, viz.: Potash, soda, lime, magnesia, oxide of iron, chlorine, sulphuric acid, phosphoric acid, silicic acid, and carbonic acid. The chemical composition of different specimens of the same plant is found to be quite uniform.
VEGETABLE NUTRITION.
Young plants first feed upon the store of nourishment placed in the seed, either in cotyledons,[3] or around them. Soon the little roots acquire the power to take their nourishment from the earth in which they are imbedded. They absorb moisture and the materials in solution, which rise through the latest formed wood as ascending sap, and in the cells of the growing parts, especially the leaves, undergo the transformations which convert inorganic into organic substances. Hales[4] calculated that the force which impels the sap in a grapevine in summer time is five times as great as that which drives the blood through the arteries of a horse.
SECTION OF AN ENDOGENOUS STEM.
Much of the water is evaporated. A large sunflower was found to exhale twenty or thirty ounces during the day, but very little at night. After the sap has been elaborated in the cells, under the influence of air and light, it descends just under the bark, in the cambium layer, and furnishes the material for the growth of cells and young buds, and nourishes all growing parts of the plant. This process takes place essentially in the earlier part of the season. In late summer and autumn the circulation in the leaves is impeded by the deposition of mineral matter, so that the plant or tree becomes gorged with the fluids which are ready to flow again at the coming of spring. It is this supply which is drawn upon in the “sugar bush.” A bucketful is often obtained from a single maple tree in twenty-four hours.
The cambium layer, or mucilaginous material between the bark and wood, hardens into cellular tissue and forms an annular growth. This is the case in all exogenous plants. If a section be made of one of them its age may be easily determined by counting the rings. The other great class of plants called endogenous, has the growing masses distributed through the stem. The common cornstalk is an illustration. Few things are more surprising than the way in which different plants manufacture from the same elements their
VARIOUS PRODUCTS.
This is noticeable in grafting. I have seen a thorn bush having one limb loaded with Bartlett pears. Now the material which ascended the stem was distributed to all the branches, but the cells in some of them manufactured it into thorn apples, while in this branch it was transformed into delicious fruit.
SHOWING A CYCAS, A YUCCA, TWO COCOANUT PALM TREES, AN INDIAN CORN STEM, AND A BANANA.
No doubt plants have the powers to select various materials. Upon the same acre of land a hundred different plants may feed and manufacture as many varieties of products, sweet, bitter, sour, poisonous, nutritious, fragrant, offensive, green, yellow, red, and so on through the entire list. As has already been suggested, many vegetable products which are quite diverse in character, are either identical or quite similar in chemical composition. Starch, whether obtained from the potato, the root of the carrot, the kernel of corn, the leaves of the cabbage, or the cotyledons of the bean, is composed of six atoms of carbon, ten atoms of hydrogen, and five atoms of oxygen. Sago, tapioca, bread fruit, arrowroot, and scores of other plant products have the same proportions. Woody fiber whether from the root, stem or branch, woven into cloth, built into houses, twisted into rope, made into paper, used as fuel, or manufactured into furniture, is C₆H₁₀O₅.
Slight variations in composition often produce marked differences. The introduction of the least ferment into sugar (C₆H₁₂O₆) would break it up into two deadly poisons, alcohol (2C₂H₆O) and carbonic acid gas (2CO₂—two molecules of each). A slight addition of oxygen spoils all the sweetness of the preserves.
The rhubarb manufactures oxalic acid, the grape tartaric acid, the apple malic acid, the lemon citric acid, the oak tannic acid, from carbon, hydrogen and oxygen, by simply varying the number of their atoms.
If we add one atom of oxygen (C₁₀H₁₆O) to the constituents of the volatile oils previously mentioned, we form a new group comprising camphor, wintergreen, spearmint, cinnamon, bitter almonds, and many others.
Notwithstanding the great uniformity in the composition of various vegetable products, it is now well understood that one crop may restore to land what another has removed, hence the modern agricultural doctrine of
ROTATION OF CROPS.
In southeastern Virginia you find many pine forests in which may be traced the ridges of the corn rows. These fields were planted with corn continuously, until the soil became so impoverished that it would not yield a crop. They were then abandoned and allowed to grow up to pines.
A better system would have secured perpetual fertility. The soil of England produces far more than formerly, even after the cultivation of a thousand years. China furnishes a still more remarkable example of productiveness.
The amount of the earth’s crust which is concerned in the support of life is exceeding small. The natural tendency is constantly to diminish this.
Rains and rivers bear away the best of the soil and deposit it in the lakes and seas. Some inhabitant of our earth in the far future, may secure the benefit of these stores, when the beds of the present seas and oceans shall have risen above the waters and become the continent.
Too much pressed by the demands of the present to even think of this, the wise farmer endeavors to return to his soil what it has lost.
Growing crops are plowed under, fertilizers from the thronging cities are spread upon his fields, the seaweed cast up by the waves yields its potash, phosphorus, salt and iodine. The islands of the Pacific contribute their vast stores of ammonia accumulated for ages in guano beds; marl deposited in the estuaries of ancient geologic seas feeds the cereals; and the limestone deposits are made to give verdure to the grasses of a thousand meadows. In the meantime, nature has her own processes of restoration. The crumbling of the rocks by frost, their abrasion by water, the accumulation of humus by decay, and various chemical influences conspire to convert the unproductive rocks into fertile soil. It would seem that this intelligent forethought, united with the beneficent processes of nature may secure perpetual productiveness, to the end that the earth may continue to yield its increase for the sustenance of the animal, for, as the Scriptures say,
ALL FLESH IS GRASS.
Directly or indirectly all animals live on plants. We have roast lamb for dinner to-day, but yesterday the lamb was browsing herbage. It is an interesting fact that the nutritive qualities of bread are almost the same as those of beef—each, in itself, is very nearly a perfect food.
LEAN MEAT.
Great principles of economy regulate the use of these two articles, in accordance with the scarcity and price of either. Man may live without bread if he have meat, and vice versa, but his system demands one of them, or its equivalent.
As in the cell of the plant, mineral substances become organized, so, under the influence of animal vitality does vegetable material become transformed into the constituents of a new organism. The great argument against the doctrine that alcohol is a food, lies in the fact that it does not undergo this transformation. It leaves the body as it enters it. But beef-steak ceases to be steak, and bread is no longer the same; they have become bone, tissue, nerve, and all that makes a human body
Most are familiar with the marvelous processes of mastication, digestion, absorption and aeration, by which food is converted into blood freighted with all that is essential to the nutrition of the human system.
A COLUMN, ARCHES, DOMES, SPIRES AND MINARETS.
Foods serve three great purposes—growth, restoration of waste, and supply for heat. Whether vegetable or animal, they are of two classes—nitrogenous and carbonaceous. The former consists of all seeds and vegetable tissues, and flesh in animal foods. The latter comprises the starch and sugar of vegetables, and fat in animals. Nature seems to suggest the propriety of using both as food for man. His teeth are adapted to the mastication of both, and the varied demands of different seasons and climates furnish a not less conclusive argument in its favor.
It is not our design to discuss here the dietetics or even the chemistry of food. There is, however, one branch of the subject that calls for a passing remark—the value of foods for special purposes. As the agriculturist is now carefully considering the adaptation of soils to the various kinds of vegetation, and is also inquiring into the character of those fertilizers that will continue and increase the growth-producing qualities of his land, so the physiologist is seeking to discover the special value of different aliments for all conditions of health and disease. The problem is necessarily somewhat difficult, but the end is so desirable—nothing less than human safety, comfort and development—that it is one of the most worthy of all the questions of science. Wholesome food, cheap food, and appropriate food for all classes and conditions is its aim. What does the weary brain require? What will give strength to muscle? How may the impoverished blood be enriched? How can vigorous, symmetrical growth be secured to childhood and youth? These are vital questions. Even when applied to the wants of the lower animals they are of immense importance. What conditions are most favorable for fattening cattle? What will give greatest strength and best sustain continuous exertion.
Note a simple instance of one result of such inquiry. In ascertaining the food value of cottonseed, the revenue of our cotton crop is said to have been doubled. In medical practice physicians are more and more inclined to depend upon their knowledge of the principles of alimentation and the adjustment of proper nourishment to the sick than upon artificial stimulants or medicines.
THE CIRCLE COMPLETED.
We conclude this article on the chemistry of organisms, with the somewhat humbling reflection that to all living beings there comes a time when vitality yields to the power of those chemical forces, which resolve them again to their original inorganic forms. It can not be that this was the only and ultimate end contemplated by the Creator, in that sublime system of arrangement for life, which began with the morning of creation and ended with man. Nature is more than a cycle of change from dead matter to vegetable form, thence to animal life, and thence back again to mineral substance.
Solomon wrote: “The dust shall return to the earth as it was, and the spirit shall return unto God who gave it;” and another has said: “There remains the paramount duty of rendering worthy of survival that spiritual part of our being which no merely physical power can destroy.”