Page:Popular Science Monthly Volume 21.djvu/725

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danger M. Gautier advises avoidance of everything that can raise a dust of leaden compounds, of all unnecessary direct contact with lead and its preparations, scrupulous care for the cleanliness of person, clothing, tools, face, and mouth, and observance of general hygienic rules and temperance.

Disadvantages and Advantages of Bacteria.—In a paper on "Bacteria in Healthy Individuals," Surgeon George M. Sternberg, of the United States Army, considers the question, which many have been ready to ask, If bacteria are such terrible things, how is it possible that we can exist upon the earth, surrounded and infested as we are by them? "Certainly," says Surgeon Sternberg, "there would be an end to all animal life, or rather there would never have been a beginning, if living animals had no greater resisting power to the attacks of these parasites, which by numbers and rapid development make up for their minute size, than has dead animal matter." The obvious answer to the question, that living animals have the required superior resisting power, is supported by Pasteur's researches, which show that it depends very much upon certain well-defined circumstances whether the same bacterium is a harmless parasite and commensal of man and animals, or an active agent promoting disease and decay. "Nature," says Dr. Sternberg, "has placed in the living tissues of animals a resisting power against the encroachments of bacterial organisms invading and surrounding them, which is sufficient for ordinary emergencies. But when the vital resistance of the tissues is reduced, on the one hand, by wasting sickness, profuse discharges, etc., or, on the other hand, the vital activity of the invading parasitic organism is increased, the balance of power rests with the infinitesimal but potent micrococcus. . . . Experiment has demonstrated that, by some unknown mechanism, the ordinary bacteria of putrefaction, and, under certain circumstances, even pathogenic organisms, may be introduced directly into the circulation without the production of evil consequences, and that after a short interval microscopical examination does not reveal their presence in the blood." There is compensation for the damage wrought by bacteria, which is described by Dr. Sternberg with some exaggeration, and hardly sufficient consideration of the power of the normal chemical forces of nature, in these words: "On the other hand, but for the power of these little giants to pull to pieces dead animal matter, we should have dead bodies piled up on all sides of us in as perfect a state of preservation as canned lobster or pickled tongue, and there being no return to the soil of the materials composing these bodies, our sequoias and oaks would dwindle to lichens and mosses, and finally all vegetation would disappear, and the surface of the earth would be a barren and desolate wilderness, covered only with the inanimate forms of successive generations of plants and animals."

Variable Stars.—Professor A. Ritter attempts, in his recent work on the "Application of the Mechanical Theory of Heat to Cosmological Problems," to explain the 1 origin and nature of variable stars by supposing that, stable as they appear to our i limited vision, the planetary systems are. subject to ceaseless recurring changes, in the course of which they go through all the phases of cosmical evolution. The speed I of the revolutions of the several members of the systems being constantly retarded by the resistance of the ether, they eventually yield to the attraction of the central body and fall into it. The concussion generates heat enough to resolve the whole mass into a vapor or gas which diffuses itself through space till its surplus heat is so dissipated that the attractive force is able to overcome its power of expansion, when the vapors begin to contract, and consequently to develop heat anew. The internal heat of the contracting body at last becomes strong enough to overcome the force of gravitation, and a new expansion begins. The gaseous sphere is thus subjected to a movement of rhythmical pulsation, the temperature increasing with the contractions and diminishing with the expansions, and will appear from a distance, if the variations in temperature reach a certain degree, alternately bright and dark, or as a variable star. The duration of the pulsations will vary according to the size of the body, and the period will bear a certain relation to its density; so that we may deduce one of the