PATHOGENIC BACTERIA.

PART I. GENERAL CONSIDERATIONS.

INTRODUCTION.

THE unrecognized inception of the department of science which we are about to study had its latent germs in the thought of antiquity.

It is folly to begin the consideration of bacteria with their probable discoverer, Leeuwenhoek, or with the socalled "Father of bacteriology," Henle. The controversies and ideas which stimulated the investigations and researches which have brought us to our present state of knowledge were begun hundreds of years before the beginning of the Christian era.

Excepting such as taught and believed that "in six days the Lord made heaven and earth, the sea and all that in them is," or a kindred theory of the origin of things, the thinkers of antiquity never seem to have doubted that under favorable conditions life, both animal and vegetable, might arise spontaneously.

Among the early Greeks we find that Anaximander (43d Olympiad, 610 B. C.) of Miletus held the theory that animals were formed from moisture-an idea that would stamp him a disciple of Thales if we did not know that his doctrine was that "the Infinite is the substance of all things." Empedocles of Agrigentum (450 B. C.) attributed to spontaneous generation all the living beings. which he found peopling the earth. Aristotle (B. C. 384) is not so general in his view of the subject, but asserts

that "sometimes animals are formed in putrefying soil, sometimes in plants, and sometimes in the fluids of other animals." He also formulated a principle that "every dry substance which becomes moist, and every moist body which becomes dried, produces living creatures, provided it is fit to nourish them."

Three centuries later, in his disquisition upon the Pythagorean philosophy, we find Ovid defending the same doctrine:1

"By this sure experiment we know

That living creatures from corruption grow:
Hide in a hollow pit a slaughter'd steer,

Bees from his putrid bowels will appear,

Who, like their parents, haunt the fields and bring
Their honey-harvest home, and hope another spring
The warlike steed is multiplied, we find,

To wasps and hornets of the warrior kind.
Cut from a crab his crooked claws, and hide
The rest in earth, a scorpion thence will glide,
And shoot his sting; his tail in circles toss'd
Refers the limbs his backward father lost;

And worms that stretch on leaves their filmy loom
Crawl from their bags and butterflies become.
The slime begets the frog's loquacious race;
Short of their feet at first, in little space,

With arms and legs endued, long leaps they take,
Raised on their hinder part, and swim the lake,
And waves repel; for nature gives their kind,
To that intent, a length of legs behind."

Not only was the doctrine of spontaneous generation of life current among the ancients, but we find it persisting through the Middle Ages, and descending to our own generation to be an accidental but important factor in the development of a new branch of science. In 1542, in his treatise called De Subtilitate, we find Cardan asserting that water engenders fishes, and that many animals spring from fermentation. Van Helmont gives special instructions for the artificial production of mice,

1 Ovid's Metamorphoses, translated by Mr. Dryden, published by Sir Samuel Garth, London, 1794.

and Kircher in his Mundus Subterraneus (chapter "De Panspermia Rerum ") describes and actually figures certain animals which were produced under his own eyes by the transforming influence of water on fragments of stems from different plants.1

About 1668, Francesco Redi seems to have been the first to doubt that the maggots familiar in putrid meat arose de novo: "Watching meat in its passage from freshness to decay, prior to the appearance of maggots, he invariably observed flies buzzing around the meat and frequently alighting on it. The maggots, he thought, might be the half-developed progeny of these flies. Placing fresh meat in a jar covered with paper, he found that although the meat putrefied in the ordinary way, it never bred maggots, while meat in open jars soon swarmed with these organisms. For the paper he substituted fine wire gauze, through which the odor of the meat could rise. Over it the flies buzzed, and on it they laid their eggs, but the meshes being too small to permit the eggs to fall through, no maggots generated in the meat; they were, on the contrary, hatched on the gauze. By a series of such experiments Redi destroyed the belief in the spontaneous generation of maggots in meat, and with it many related beliefs."

It was not long before Leeuwenhoek, Vallismeri, Swammerdan, and others, following the trend of Redi's work, contributed additional facts in favor of his view, and it may safely be asserted that ever since the time of this eminent man the tide of scientific opinion has turned more and more strongly against the idea that life is spontaneously generated.

About this time (1675) one whose name has been already mentioned, Anthony van Leeuwenhoek, and who is justly called the "Father of microscopy," came into prominence. An optician by trade, Leeuwenhoek devoted much time to the perfection of the compound microscope, which was just coming into use. The science of 1 See Tyndall: Floating Matter in the Air.