just arching his horns upon his forehead of two years old, is sought out; whilst he struggles fiercely, they close up both his nostrils and his mouth; and when they have beaten him to death, his battered carcass is macerated within the hide which remains unbroken. Then they leave him in the pent-up chamber, and lay under his sides fragments of boughs, thyme and fresh cassia. This is done when first the zephyrs stir the waves, before the meadows blush with new colors, before the twittering swallow suspends her nest upon the rafters. Meanwhile, the animal juices, warmed in the softened bones, ferment; and living things of wonderful aspect, first devoid of feet, and in a little while buzzing with wings, swarm together, and more and more take to the thin air, till they burst away like a shower poured down from the summer clouds; or like an arrow from the impelling string, when the swift Parthians first begin to fight.”

The following quotation from Ovid may not be beside the mark:

"By this sure experiment we know

That living creatures from corruption grow;
Hide in a hollow pit a slaughtered 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't
Refer 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 a little space.

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

From even casual examination of these quotations it is easily evident that there was a quaint confusion between cause and

effect and hardly an attempt at critical analysis. Facts were facts, regardless of their incongruity. And yet it seems strange from our modern point of view that keen observers as some Greeks undoubtedly were they failed to see the fallacy of their observations. However, many years were to pass before even descriptive biology was to be rid of its many fallacies. That maggots came from cheese and that crocodiles came from the mud of the Nile were accepted as facts by the natural philosophers. Van Helmont is said to have published "special directions for tht experimental generation of mice," and Athenasius Kircher, as late as 1659, "demonstrated the presence of 'minute living worms in putrid meat, milk, vinegar, etc'; but he did not describe their form and character, and it is doubtful if he ever saw microorganisms."

About a decade later Redi reported his observations which struck a notable blow in demolishing the false structure that had been very elaborately developed through a period of many centuries. By means of a simple but carefully controlled series of experiments he successfully demonstrated the fallacy of assuming an etiological relationship between putrefying meat and maggots. Heretofore it had been considered sound logic to profess that the maggots had been generated in the meat because their presence was so frequently observed when the meat became putrid. Redi, however, noted in addition the almost invariable presence of flies darting here and there over and occasionally alighting on the flesh. He conceived the possibility of considering the maggots as immature flies and of attributing their presence to the buzzing adults. He pointed out that if two jars of meat are set side by side, one covered with paper, and the other left uncovered, and both permitted to putrefy, both will attract flies, but "only the uncovered one will engender maggots."

His experiments were severely criticised on many and diverse grounds. Among other objections it was said that the paper covering on his jar had impeded the rising of the odors. Immediately a brilliant thinker decided that "odours and vapours. are essential in the bringing forth of worms and of many crawling things." Redi then repeated his experiments, substituting for the paper some fine mesh wire gauze through which the

"odours and vapours" could permeate. He had been careful, however, to choose a gauze of mesh so fine that the eggs of the flies were retained upon it and failed to reach the meat. The eggs, of course, hatched out on the gauze. The meat continued to putrefy but failed to show the presence of maggots. Redi's conclusion that maggots came from the eggs of flies, not from putrid meat, remained for a long time an almost incontrovertible proof to those who were sorely in need (though they knew it not) of instruction in scientific reasoning.

In the century following, but little new was added and the old was hardly raked over. Here and there, occasional observers cropped up who dared think for themselves and who attempted to disenfranchise their thoughts from the fallacies and sophistries of their predecessors. It is true, unfortunately, that even they erred at times. On the whole, one might have also expected continued and valuable advance in the 18th century toward a true understanding of natural phenomena. However, a new era had been opened by the observations and experiments of a group of inquisitive men, armed with a new and powerful instrument-the microscope. How their work helped at first to give a new lease of life to the conception of "spontaneous generation" instead of aiding in the overthrow of its tenets goes to make up one of the most interesting chapters in the history of Biology.

As early as 1680 Anton von Leeuwenhoek, a Dutch microscopist, had examined a great variety of substances with the aid of his new and improved microscope, so constructed as to magnify objects about 150 diameters. He described the appearance of certain dot-and-dashed-shaped "animalcula" which he could detect in water, saliva, and tartar from teeth. He even made the very interesting observation that the tartar scraped from the teeth of an old man who had not developed rigid habits of cleanliness showed more numerous and more varied motile animalcula than that obtained from the teeth of a young lady. Though it can hardly be asserted that Leeuwenhoek considered these exceedingly small objects living things, it is certainly true that he studied them quite carefully. In the thirty years following there was developed an opinion that the small microscopic forms were living things and that they represented the very

threshold of life. For a great many years it had been exceedingly difficult to hold the ground that living things were formed in a manner neither spontaneous nor divine. But here, in the discovery of the micro-organisms, was the key to this puzzle of the philosophers. Though it might have been difficult for many to imagine the spontaneous appearance of highly evolved animals, it was another matter when one considered these apparently simple and elementary forms. (I say apparently simple, for to-day we know that even the bacteria are highly complex cells, considered from both the morphological and physiological points of view.)

In the years 1745-1750 the English divine Needham published his experiments on the spontaneous appearance of bacteria on germinated barley grains kept in a very carefully covered watchglass. Twenty-five years later the brilliant Abbé Spallanzani attacked the experimental technique as well as the conclusions of the earlier workers. "He supposed that he had proved spontaneous generation impossible by a new and improved technique. He filled flasks with various organic infusions, such as were sup posed to be 'biogenic,' subjected the contents to thorough boiling, hermetically sealed them, and then placed them under what were supposed to be conditions favorable to the development of life, but always with negative results. Instead of carrying conviction with them, these experiments of Spallanzani were severely criticised by Treviranus on the ground that the atmosphere, so essential to life, had been excluded from the fluids. To overcome this objection Spallanzani gently tapped his flasks so as to produce minute cracks through which air might enter. When this was done, life invariably appeared and decomposition occurred." Thus while the Abbé's major premise was correct (as we look upon it to-day), nevertheless he failed to establish it, because he did not recognize that in air there were suspended germs which it was essential to exclude.

In 1836, Franz Schultze demonstrated that if air was successively passed through a series of bulbs containing strong acids or alkalies, and then into flasks filled with boiled, putrescible liquids, no putrefaction set in; the caustics had destroyed the living organisms contained in the air. The following year Theodor Schwann presented his classical paper on his studies of put

refaction and fermentation. To remove living organisms from air he improved upon Schultze's method by passing the air through heated tubes. In order to prove that heating the air did not rob it of certain properties which it was believed to possess and which were believed to play an important part in fermentative processes, he conducted another series of experiments. To his great surprise he found that air passed through heated tubes into flasks containing liquids capable of undergoing vinous fermentation did not initiate the fermentation. The explanation was that he had boiled his liquid and had killed the yeast. His studies led him into developing a new series of experiments, and these in turn led him to attribute putrefaction to the presence of living germs in air. The results of his studies with yeast pointed to the conclusion that "alcoholic fermentation was also brought about by a living organism, a conception which was at once confirmed by a microscopical examination of a fermenting liquid.” In the same year Cagniard-Latour and Kützing, each independently, came to virtually the same conclusions.

The papers of the three experimenters were published almost simultaneously and at first made many people of the scientific world gasp. Very shortly afterwards, Berzelius, the arbiter of the chemical world, reviewed them in his Jahresbericht (1839) with impartial scorn. Then followed the very important conflict between Berzelius and Liebig on the one side and the followers of Cagniard-Latour, Schwann and Kützing on the other. In his "Memoire sur le cause les effets de la fermentation alcoholique et aceteuse" (1839), the result of a request from the Academy of Sciences for an investigation, Turpin expressed himself as satisfied with the accuracy of Cagniard-Latour's conclusions. In the same year Wöhler and Liebig published in the latter's "Annalen" an elaborate skit in which "yeast was described with a considerable degree of anatomical realism as consisting of eggs which developed into minute animals, shaped like a distilling apparatus, by which the sugar was taken in as food and digested into carbonic acid and alcohol, which was separately excreted, the whole process being easily followed under the microscope." The more serious criticisms of Liebig and his colleagues failed however to shake the foundation of the structure which was being built up.