son used for comparative purpose a crop of rye yielding 32 bushels of grain and 3800 pounds of straw, corn yielding 75 bushels of grain and 8000 pounds of stalks and leaves, 2 tons of hay, and 300 bushels of potatoes. Davidson compared the yield of 1000 pounds of Virginia leaf per acre (and 353 pounds of stalks) with 30 bushels of corn and stover, or oats, 30 bushels and straw:

Table II.-PLANT FOOD REMOVED FROM AN ACRE OF LAND BY TOBACCO AND OTHER CROPS.

Under a rational system of husbandry, cornstalks, oat straw, wheat straw and hay are fed to stock, and their ingredients return to the soil in manure, just as tobacco stalks return to the land. Hence, we should only compare plant food removed in the grain alone with that taken off in the tobacco leaf alone. Rye straw, however, is usually sold, also potatoes, so that the total quantity these crops take from the soil may be compared with the plant food in tobacco leaf.

Table III.-POUNDS OF PLANT FOOD TAKEN FROM THE SOIL BY AVERAGE YIELDS PER ACRE OF SO MUCH OF TOBACCO AND OTHER CROPS AS IS NOT RETURNED TO THE LAND.

It appears that the full yield of Connecticut tobacco takes from the soil less nitrogen than a good crop of corn grown under similar conditions, but little more than potatoes, but twice as much as rye. Of potash, tobacco takes even less than potatoes, but several times as much as corn or rye. Of phosphoric acid the other

crops take two or three times as much as tobacco. In Virginia leaf, the same relative proportions hold, though the quantities differ, the average crop of tobacco taking about the same quantity of nitrogen, nearly five times as much potash, but only one-third as much phosphoric acid as a wheat crop of thirty bushels per acre.

SOME RELATIONS OF BACTERIA TO TOBACCO CURING AND MANUFACTURE.

BY WILLIAM FREAR.

There are several distinct classes of organisms to whose activity the various fermentations are traced. First among these may be named the molds, distinguished by the formation of a closely interwoven network of white, thread-like cells, or hyphæ; from this network, or mycelium, spring little stalks, swelling or branching into larger heads; these heads, in turn, bear the colored spores, or reproductive elements, appearing as a fine dust upon the upper surface of the grayishgreen or black molds to which jellies, cheese and bread kept in damp places are subject. Molds also multiply by the branching out of new hyphæ, affording the root from which new stalks may spring.

Another class of organized ferments is that to which yeast belongs. The organism is much simpler in these cases than in the molds. It is composed of only a single cell, or papery sac, filled with jelly-like protoplasm. This protoplasm carries on, however, most of the func tions of more highly organized beings. Yeasts reproduce by budding,-the sprouting from the side of the

parent cell of a little, bubble-like offshoot; this, when sufficiently developed, detaches from the parent and assumes an independent existence.

Most important of all is that class of ferments known in general as bacteria. There are many species of these, differing in shape, mode of aggregation, conditions of life and products. If a liquid containing bacteria be examined, it will often be found swarming with these little organisms, ranging from 3 to less than ʊʊʊ of an inch in size, according to the species. The little beings are not quiet, but are vigorously active.

Reproduction of the various species is accomplished in two ways: First, by fission, or the splitting in half of the single-celled parent; the small halves then separate and grow to full size. Second, many species develop within the body of the parent a number of thick-walled bodies, or spores, which are later discharged, and which, under favoring conditions, develop into the normal, mature bacterium.

Most important features of these organisms are their wide distribution and their wonderfully rapid multiplication. Though requiring a certain amount of moisture for their active life, they are not destroyed by slow drying at a low temperature. In consequence, they are carried as dust by every passing wind, to new lodging places, where they develop if the conditions are favorable. As, under most favorable conditions, the individuals of some species can reproduce in twenty minutes after their own birth, it is a simple arithmetical process to show that a very short time would suffice for them to occupy the globe. Such favorable conditions never occur; but the multiplication often observed is, nevertheless, tremendous; and the fermentative changes produced are correspondingly great.

The conditions surrounding them greatly influence their activity and multiplication. Some require free

access to air, and are called aerobes, in consequence; others, when cut off from the air, are able to obtain from oxygen-containing compounds all of this element they require for respiration; such are called anaerobies. Usually, bacteria require a slightly alkaline medium for their development; only a few can survive in an acid liquid; whereas, molds require the latter medium for their best. growth. When, therefore, the lactic ferment, which sours milk, and the nitrifying ferment, which forms nitric acid in the soil, have produced an excess of acid, they cease to act until the excess is neutralized, when they renew their production of acid. Vinegar, therefore, serves as a preventive of bacterial fermentation in food preparations. Other substances, conspicuously carbolic acid, copper and mercury salts, similarly prevent the action of bacteria, and destroy them.

In general, 100° F. is above 150° F. few are The process of pasteur

While diffuse light is not fatal, direct sunshine is the most destructive natural foe of these ferments. They require for their best action certain temperatures, varying for different species. most favorable; below 50° and active, and many are destroyed. izing milk by heating to 150° for thirty minutes is based upon this fact. Some bacteria, and especially spores, which are more resistant, owing to their thick walls, are not killed by dry temperatures as low as 315° F., or above 212°, the boiling point of water; very few, however, withstand the latter temperature if they be moist; consequently, boiling the liquid containing them, or steaming them, are among the most commonly employed methods of sterilization of liquids or solids-that is, the destruction of the bacteria the latter contain.

Bacteria differ, not only in these respects, but in the color, form and consistency of the colonies they make in various liquid and solid media.

The most sharply distinctive characteristic, how

ever, and that most frequently useful for their determi nation, is that the products they form are distinctly different. Some liberate gas, and the gases from various species differ in composition. In other cases, substances of pronounced odor or flavor are developed, as in the putrefactive fermentations, and in those of ripening cheese and ripening cream. The disease germs accomplish their fatal results, it is now believed, more frequently through the poisons they form in the blood-poisons similar, chemically, to the active principles of snake venom-than through any direct action of their own.

Ordinarily, the conditions favorable to the development of one species of bacterium are also such as permit the development of other species. Hence, under natural conditions, a single species rarely occurs alone. By selection of the most congenial nutritive medium for a given species of which it is desired to secure a pure culture, that is, a colony in which no foreign species exists, and by regulation of temperature so that that most favorable to the species in question may be maintained, it is possible to gradually eliminate undesirable species from a series of cultures, and secure a culture in which only the species desired remains. The process is much hastened, first, by using a sterilized culture medium and sterilized apparatus; second, by preventing access of foreign germs from the air-this is accomplished by filtering the air to which the solution is exposed, through cotton-wool, or some similar substance, which removes all floating dust from the air, including the dried germs; third, by diluting the primary material from which the germs are taken, and using a very small quantity of the diluted substance to act as a starter for the new solutions; often, this process introduces into some of the cultures very few, if any, foreign species, so that these cultures may be made the basis of further operations, and others, less pure, be rejected at once.