also showed, all life comes from antecedent life of the same kind—a fact of far-reaching importance in elucidating the phenomena of fermentation and disease.

How the gap between the inorganic and the organic world was originally crossed remains an unsolved problem. The study of microscopic organisms, with the greatly improved methods of modern technique, has revealed complexities of structure which were unsuspected by the older observers. To suppose that such forms as Infusoria, for instance, arose spontaneously out of lifeless compounds, is much like supposing that a house should suddenly build itself out of a pile of bricks. It is not improbable that the exceedingly minute forms known as the filterable viruses are much more simple than any of the organisms with whose structure we are acquainted. But there is a wide difference between the simplest imaginable living creature and the most complex compound that can be fabricated by the chemist. Beginning with the synthesis of urea out of inorganic constituents by Wöhler, in 1828, organic chemists have built up one organic compound after another, going on, step by step, from the simple to the complex, until many of the carbohydrates and some of the simple proteins are now artificially synthesized in the laboratory. Whether chemists will ever succeed in fabricating living protoplasm it would be unsafe to predict. If they do, it would seem probable that the same transformation has been effected in nature, perhaps many times. A few scientists, Helmholtz, Lord Kelvin, and more recently, Arrhenius, have suggested that minute forms of life may have been wafted to the earth from other parts of the universe. More or less foreign matter rains down upon our planet from somewhere in interstellar space, and if some of it came from other worlds that support life, it is of course possible that very primitive organisms might have been carried by this means to our earth. This theory, however, only puts the solution of the problem back a little, although it is possible to maintain, as Ritter has done, that life might never have originated at all, but has been traveling about the universe from pillar to post throughout all eternity.

I do not see how this hypothesis can be definitely disproven, although this is not necessarily saying much in its favor. A more widely accepted view among biologists is that living matter is the product of a slow evolution from inorganic materials. There have been several hypotheses as to how the transition might conceivably have been made, but the subject is still in a highly speculative stage. It may long remain so before the problem is finally settled, or the next few years may bring discoveries that place it in an unexpected light.

REFERENCES

ABBOTT, A. C., Principles of Bacteriology. Philadelphia, Lea and Febiger, 1905.

CALKINS, G. N., Protozoology. Philadelphia, Lea and Febiger, 1909. JENNINGS, H. S., The Behavior of Lower Organisms. N. Y., Columbia University Press, 1906.

JORDAN, E. O., General Bacteriology (7th ed.). Philadelphia, Saunders, 1923.

MARSHALL, C. E., Microbiology. Philadelphia, Blakiston, 1911.

MINCHIN, E. A., An Introduction to the Study of the Protozoa. London, Arnold, 1912.

MUIR, R., AND RITCHIE, J., Manual of Bacteriology (7th ed.). London, Frowde, Hodder, and Stoughton, 1919.

TYNDALL, J., Essays on the Floating Matter of the Air. London, Longmans, Green, 1881.

Fragments of Science, and New Fragments. N. Y., Appleton,

SIMS WOODHEAD, G., Bacteria and Their Products. N. Y., Scribner,

1891.

CHAPTER VI

MICRO-ORGANISMS AND DISEASE

The study of the one-celled forms of plant and animal life has led to one of the greatest achievements in the history of science—the discovery of the causes of contagious and infectious diseases. For ages the reason for the spread of infections and epidemics remained a complete mystery. Among primitive peoples in general, disease is interpreted as due to the activities of spirits which invade the body of the afflicted person. If these spirits are of evil intent they may make all sorts of trouble, and there is no relief until they take their departure. In accordance with this theory, which is a natural corollary of the belief in animism that prevails so widely among uncivilized peoples, the treatment of disease consists in supplications, threats, incantations, magic rites, and various other devices by which the intruding spirits may be induced or forced to leave the body of their victim. In the state of knowledge that obtains among primitive men, the doctrine of animism is a perfectly reasonable theory, and the practices based upon it follow quite naturally. Even the literature of civilized peoples is full of indications of the belief in demoniacal possession, a Church of England baptismal formula of the time of Edward VI containing the words "I command thee, unclean spirit, in the name of the Father, the Son, and of the Holy Ghost, that thou come out and depart from these infants."

But amid the well-nigh universal prevalence of the doctrine of demoniacal possession, we find back in the period of greatest development of Greek thought, in the fifth century before Christ, the beginnings of a scientific theory of medical treatment. The great Hippocrates, deservedly known as the founder of medicine, taught that disease is the result of natural causes and should be

treated by natural means. In the succeeding centuries the healing art came to fall more and more within the province of science. Efforts were made to discover what produces abnormal conditions in the body, but the problem of the transfer of disease baffled all attempts at solution. In an epidemic which spreads over a population there is apparently something which passes from one person to another which causes the malady to develop. By some it was thought to be "morbid matter"; by others a kind of movement analogous to a vibration, but none of the theories really threw any light upon the mysterious phenomenon. Until nearly the last quarter of the nineteenth century, the cause of contagion was as much of an enigma as it was in the days of Hippocrates.

The so-called germ theory of disease had been entertained more or less seriously ever since the first discovery of minute forms of organic life, but it remained for a long time a mere plausible conjecture, unsupported by experimental evidence. Pasteur's work on fermentation and spontaneous generation, and his successful attack upon the diseases of wine and beer, naturally disposed him, as it did several of his contemporaries, to look with favor upon the doctrine that infectious diseases might result from the presence of micro-organisms. In the course of his work he had often reflected upon the prophetic remark, made over two hundred years before, by the English chemist, Robert Boyle, that "he that thoroughly understands the nature of ferments and fermentation shall probably be much better able than he that ignores them to give a fair account of the diverse phenomena of several diseases." Pasteur's studies on the diseases of silkworms, which resulted in connecting these maladies with the presence of specific micro-organisms, served to give further support to the germ theory. In Scotland the celebrated physiologist, Joseph Lister, who had followed Pasteur's work on fermentation and spontaneous generation with the keenest interest, came to the conclusion that the cause of infections, which in those days so frequently resulted from surgical operations, was to be sought in micro-organisms which gained access to the

wounds from the hands and instruments of the operator, or from the floating matter of the air. Accordingly Lister insisted on having everything connected with a surgical operation thoroughly sterilized. The hands of the surgeon, the instruments, and the bandages employed were washed in a solution of carbolic acid, and dressings, sterilized in the same solution, were applied to the wound. As a result of these precautions, the mortality from operations was reduced to a surprising extent. Previously, wounds almost always became charged with pus, and very commonly developed gangrene and were followed by general blood poisoning. Hospitals were hotbeds of infection that greatly decreased a patient's chances of successful recovery. All operations which involved opening the abdomen were exceedingly dangerous, and many operations for troubles that would terminate fatally if allowed to take their natural course, were almost certain to result in death at the hands of the surgeon. At the present time a great many of these operations are shorn of their former terrors. The great boon of antiseptic surgery, which has saved literally millions of lives and untold suffering, was a direct outgrowth of the development of our knowledge of the life history of micro-organisms and their rôle in fermentation and decay.

The theory that infections and epidemics are due to minute living organisms brings the phenomena of communicable diseases into relation with other biological facts. Here in a box of apples is a rotten apple which is found to have started decay in others with which it was brought into contact. If we should examine a bit of the decayed apple with the microscope, we should find it teeming with micro-organisms. The power of decay spreads like a disease from one apple to the next. If we take a drop from a fermenting cask of wine and introduce it into thoroughly sterilized grape juice, the latter will begin a fermentation which can be communicated in a similar way to any amount of new fermentable material. Robert Boyle was right. The communication of disease is essentially like the transfer of fermentation from one vat to another.