Though we can by no means pretend to account for the appearance of most animalcula, yet we cannot help observing, that our ignorance of the cause of any phænomenon is no argument against its existence. Though we are not, for instance, able to account in a satisfactory manner for the origin of the native Americans, yet we suppose Buffon himself would reckon it absurd to maintain, that the Spaniards on their arrival there found only ORGANIC PARTICLES moving about in disorder. The case is the very same with the eels in paste, to whose animation he objects. They are exceedingly small in comparison with us; but, with the solar microscope, Baker has made them assume a more respectable appearance, so as to have a diameter of an inch and an half, and a proportionable length. They swam up and down very briskly; the motion of their intestines was very visible; when the water dried up they died with apparent agonies, and their mouths opened very wide. Now, were we to find a creature of the size of this magnified eel gasping in a place where water had lately been, we certainly should never conclude it to be merely an ORGANIC PARTICLE, or fortuitous assemblage of them, but a fish. Why then should we conclude otherwise with regard to the eel in its natural state, than that it is a little fish? In reasoning on this subject, we ought ever to remember, that however essential the distinction of bodies into great and small may appear to us, they are not so to the Deity, with whom, as Baker well expresses himself, “an atom is a world, and a world but as an atom.” Were the Deity to exert his power a little, and give a natural philosopher a view of a quantity of paste filled with eels, from each of whose bodies the light was reflected as in the solar microscope; our philosopher, instead of imagining them to be mere organic particles, as the paste would appear like a little mountain, he would probably look upon the whole as an assemblage of serpents, and be afraid to come near them. Whenever, therefore, we discover beings to appearance endued with a principle of self-preservation, or whatever we make the characteristic of animals, neither the smallness of their size, nor the impossibility of our knowing how they came there, ought to cause us to doubt of their being animated.
I shall here insert some extracts of the experiments made by Ellis at the desire of Linnæus, and which are a full refutation of those made by Needham and Münchhausen. By those he made on the infusions of mushrooms in water, it appeared evidently that the seeds were put in motion by minute animals, which arose on the decomposition of the mushroom; these, by pecking at the seeds, which are little round reddish bodies, moved them about with great agility in a variety of directions, while the little animals themselves were scarce visible till the food they had eaten discovered them.
The ramified filaments, and jointed or coralloid bodies, which the microscope discovers to us on the surface of most vegetable and animal infusions, when they become putrid, and which were supposed by Needham to be zoophytes, were found by Ellis to be of that genus of fungi called mucor, many of which have been figured by Michelius, and described by Linnæus. Their vegetation is so quick, that they may be seen to grow and seed under the eye of the observer. Other instances of similar mistakes in Needham’s experiments may be seen in Ellis’s paper, Philos. Trans. vol. lix. p. 138.
A species of mucor arises also from the bodies of insects putrefying in water; this species sends forth a mass of transparent filamentous roots, from whence arise hollow seed vessels; on the top there is a hole, from which minute globules often issue in abundance, and with considerable elastic force, which move about in the water. It will however be found, with a little attention, that the water is full of very minute animalcula, which attack these seeds, and thus prolong their motion; but after a small space of time they rise to the surface, and remain there without any motion; a fresh quantity rises up, and floating to the edge of the water, remains there inactive; but no appearance can be observed of detached and separated parts becoming what are called microscopic animalcula. Indeed, it is surprizing that Needham should ever take the filaments of the moistened grains for any thing else than a vegetable production, a true species of mouldiness.
On the 25th of May, Fahrenheit’s thermometer 70°, Ellis boiled a potatoe in the New River water, till it was reduced to a mealy consistence. He put part of it, with an equal proportion of the boiling liquor, into a cylindrical glass vessel, that held something less than half a wine pint, and covered it close immediately with a glass cover. At the same time he sliced an unboiled potatoe, and, as near as he could judge, put the same quantity into a glass vessel of the same kind, with the same proportion of New River water not boiled, and covering it with a glass cover, placed both vessels close to each other. On the 26th of May, twenty-four hours afterwards, he examined a small drop of each by the first magnifier of Wilson’s microscope, whose focal distance is reckoned at 1⁄50 part of an inch; and, to his amazement, they were both full of animalcula of a linear shape, very distinguishable, moving to and fro with great celerity; so that there appeared to be more particles of animal than vegetable life in each drop. This experiment he repeatedly tried, and always found it to succeed in proportion to the heat of the circumambient air; so that even in winter, if the liquors be kept properly warm, at least in two or three days the experiment will succeed.
The animalcula are infinitely smaller than spermatic animals, and of a very different shape; the truth of which every accurate observer will soon be convinced of, whose curiosity may lead him to compare them, and he is persuaded they will find they are no way akin. Having learnt from M. De Saussure, of Geneva, that he found one kind of these animalcula infusoria that increases by dividing across into nearly two equal parts, and that the infusion was made from hemp-seed, he procured a quantity of this seed, some of it he put into New River water, some into distilled water, and some into very hard pump water; the result was, that in proportion to the heat of the weather, or the warmth in which they were kept, there was an appearance of millions of minute animalcula in all the infusions; and some time after some oval ones made their appearance; these were much larger than the first, which still continued. These wriggled to and fro in an undulatory motion, turning themselves round very quick all the time that they moved forwards.
Ellis found out by mere accident a method to make their fins appear very distinctly, especially in the larger kind of animalcula, which are common to most vegetable infusions, such as the terebella. This has a longish body, with a cavity or groove at one end, like a gimblet. By applying a small stalk of the horseshoe geranium, the geranium zonale of Linnæus, fresh broken, to a drop of water in which these animalcula are swimming, we shall find that they will become instantly torpid, contracting themselves into an oblong oval shape, with their fins extended like so many bristles all round their bodies. The fins are in length about half the diameter of the middle of their bodies. After lying in this state of torpitude for two or three minutes, if a drop of clean water be applied to them, they will recover their shape, and swim about immediately, rendering their fins again invisible. Before he discovered this expedient, he tried to kill them by different kinds of salts and spirits; but though they were destroyed by these means, their fins were so contracted, that he could not distinguish them in the least.[118]
[118] The preceding recital of the hypothesis of Messrs. Buffon, Needham, and Baron Münchhausen, may appear superfluous, having been so ably refuted by Mr. Ellis; the consideration, however, that it may afford entertainment to some of my readers, and prove beneficial to others, by cautioning them against too precipitately adopting plausible suppositions, induced me to retain the account. Edit.
It is one of the wonders of the modern philosophy to have invented means for bringing creatures so imperceptible as the various animalcula under our cognizance and inspection. One might well have deemed an object that was a thousand times too little to be able to affect our sense, as perfectly removed from human discovery; yet we have extended our sight over animals to whom these would be mountains. The naked eye takes in animal beings from the elephant to the mite; but below this, commences a new order, reserved only for the microscope, which comprehends all those from the mite, to those many millions of times smaller; and this order cannot be said to be exhausted, if the microscope be not arrived at its ultimate state of perfection. In reality, the greater number of microscopic animalcula are of so small a magnitude, that through a lens, whose focal distance is the tenth part of an inch, they only appear as so many points; that is, their parts cannot be distinguished, so that they appear from the vertex of that lens under an angle not exceeding the minute of a degree. If we investigate the magnitude of such an object, it will be found nearly equal to 3⁄100000 of an inch long. Supposing, therefore, these animalcula to be of a cubic figure, that is, of the same length, breadth, and thickness, their magnitude would be expressed by the cube of the fraction 3⁄100000, that is, by the number 27⁄1000000000000000, that is, each animalculum is equal to so many parts of a square inch. This contemplation of animalcula has rendered the idea of indefinitely small bodies very familiar to us; a mite was formerly thought the limit of littleness, but we are not now surprized to be told of animals many millions of times smaller than a mite; for, “there are in some liquors animalcules so small, as, upon calculation, the whole magnitude of the earth is not found large enough to be a third proportional to these minute floating animals and the whales in the ocean.”[119] These considerations are still further heightened, by reflecting on the internal structure of animalcula, for each must have all the proportion, symmetry and adjustment of that organized texture, which is indispensably necessary for the several functions of life, and each must be furnished with proper organs, tubes, &c. for secreting the fluids, digesting its food, and propagating its species.[120]
[119] Chambers’s Cyclopedia by Rees, Art. Animalcule.