ANIMALCULE, an animal so minute in its size, as not to be the immediate ob ject of our senses.
Animalcules are usuallY divided into two distinct sections, visible, and micro scopical. The first, though visible, can not be accurately discerned without the belp of glasses : the second are discover able only by the microscope. Some have supposed there are others invisible. The existence of tltese cannot well be disputed, though it cannot he asserted, unless we conclude that the microscope has not yet arrived at its highest degree of perfection. Reason and analogy give some support to the conjectures of naturalists in this re spect : animalcules are discerned of various sizes, from those which are visible to the naked eye, to such as appear only like moving points under the microscopic len ses of the greatest powers ; and it is not unreasonable to imagine, therefore, that there are others, which may still resist the action of the microscope, as the fixed stars do that of the telescope, with the greatest powers hitherto invented.
Animalcules, visible ; amongst these are included an amazing variety of creatures, by no means of analogous natures. Those numerous creatures which crowd the wa ter in the summer months changing it sometimes of a deep or pale red colour, green, yellow, &c. are of this description. 'fhe large kinds are chiefly of the insect, or vermes tribes, and of which the mono culus pulex is. particularly remarkable, being found sometimes in such abundance, as to change the water apparently to a deep red. A similar appearance is like wise occasioned by the cirearia mutabilis, when it varies in colour from green to red ; vorticella fasciculata also changes it to green ; and rotatoria to yellow. To this section we must also refer many of the acarus and h3drachna genera, and a multitude of othcr creatures that will be noticed hereafter.
Animalcules, microscopical. The micro scope discovers legions of animalcules in most liquors, us water, vinegar, beer, dew, Etc. They are also found, in rain and several chalybeate waters, and in infu sions of both animal and vegetable sub stances, as the seminal fluids of animals, pepper, oats, wheat, and other grain, tea, &c. &c. The, contemplation of animal cules has made Abe ideas of infinitely small bodies extremely familiar to, us. A mite was anciently thought the 'limit of littleness; but we are not now surprised to be told of animals tweray-seven mil lions of times smaller than a mite. Mi nute animals are found proportionably much stronger, more active and vivacious, than large ones. The spring of a flea in its leap, how vastly does it outsi rip any thing greater animals are capable of! A mite, how vastly faster does it 11111 than a race-horse ! M. de l'Islo has given the computation of the velocity of a little creature, scarcely visible by its smallness, which he found to rttn three inches in half a second: supposing now its feet to be the fifteenth part of a line, it must make five hundred steps in the space of three inches; that is, it must shift its legs five hundred times in a second, or in the ordi nary pulsation of an artery. The exces sive minuteness of microscopic.al animal cules conceals them from the human eye. One of the wonders ofmodern philosophy is, to have invented means for bringing creatures, to us so imperceptible, under our cognizance and inspection : an object a thousand times too little to be able to affect our sense should seem to have been very safe. Yet we have, extended our views over animals, to whom these would be mountains. In reality, most of our mi croscopical animalcules 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 point,s ; that is, their parts cannot be distinguished, so that they appear from the vertex of that lens under an angle not exceeding a mi nute. If we investigate the magnitude of
such an object, it will be found nearly equal to Twiizz..0- of an inch long Sup posing, therefore, these animalcules of a cubic figure, that is, of the same length, breadth, and thickness, their magnitude would be expressed by the cube of the fraction _manly, that is, by the number 27 r7t—)00,000,000,000, that is, so many parts of a cubic inch is each animalcule equal to. Leeuwenhoeck calculates, that a thousand millions of animalcula, which are disco vered in common water, are not altoge ther so large as a grain of sand. This author, upon examining the male sperm of various animals, discovered in many infinite numbers of animalcula not Liar than those above mentioned In theMilt of a single codfish there are more animals than there are, visible to the naked eye, upon the whole earth; for a grain of sand is bigger than four millions of them. The white matter that sticks to the teeth also abounds with animalcules of various figures, to which vinegar is fatal ; and it is knovin that vinegar contains animal cules hrthe shape of eels. In short, ac cording to this author, there- is scarcely any thing which corrupts without produc ing food to myriads of animalcules. Ani malcules are said to be the cause of various disorders. The itch is known to be a disorder arising-Trona the irritation of a species of acarus, or tick, found in the pustules of that ailment: when the com munication of it by contact from one to another is easily conceived, as also the reason of the cure being effected by cuta neous applications. In the Philosophical Transactions, vol. lix. is a curious account of the animalcules produced from an in fusion of potatoes, and another of hemp seed, by the late Mr. Ellis. "on the 25th of May, 1768, Fahrenheit's thermometer 70., I boiled a potatoe in the New River water, till it was reduced to a mealy con sistence. I put part of it, with an equal proportion of the boiling liquor, into a cy lindrical glass vessel, that held something less tkan a wine-pint, and covered it close immediately with a glass cover. At the same time I sliced an unboiled pota toe, and, as near as I 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 co vered with a glass cover, and placed both vessels close to each "On the 26th of May, 24 hours afterwards, I exa mined a small drop of each by the first magnifier of Wilson's microscope, whose focal distance is reckoned at 1-30th part of an inch; and, to my amazement, they were both full of animalcule, 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 I have repeatedly tried, and always found it to succeed in proportion to the heat of the eircomambient air • so that even in winter, if the liquors are kept properly warm, at least in two or three days the experiment will succeed." "I procured h emp-seed from different seeds. men in different parts of the town. Some of it I put into the New River water, some into distilled water, and some into very portion hard ump-water. The result was, that in ortion to the heat of the weather, or w. th in which they were kept, there was an appearance of millions of minute animakula in all the infusions; and, some time after, oval ones made their appear ance. These were much larger than the first, which still continued : these wrig gled to and fro in an undulatory motion, turning themselves round very quick all the time they moved forwards.