178 



ANIMALCULA. 



stituting the basis of all the muscles, ligaments, &c., 

 mill tin- most important ingredient in the composition 

 of the blood. Most of these substances are again 

 susceptible of still farther analysis, liy which they 

 may be resolved into the simple gases, as azote, 

 hydrogen, oxygen, c. ; so Uiat it appears, tliat the 

 ultimate elements of all parts of tin- visible world are 

 nearly the same in their essential character. 



ANIMALCULA, in a general sense, denotes small 

 animals. It is here used to denote one so minute that 

 its form and parts cannot be distinguished without 

 the aid of the microscope. Microscopical animals 

 may be described as more or les* translucid, destitute 

 of members, and in which no vestiges of eyes have 

 yet been discovered. They are contractile in whole 

 or in part, possessed of the sense of touch, and nourish 

 themselves exclusively by absorption. If particles of 

 animal or vegetable matter are a few days infused, in 

 the most limpid water, on applying the smallest por- 

 tion of it to die microscope, innumerable such animals 

 of various shapes are discovered. These have been 

 denominated infusory animalcules. They are also 

 found in the mud of ditches, the scum of stagnant 

 waters, &c. The origin of animalcules is a point of 

 extreme difficulty, because their existence seems 

 solely dependent on the adventitious union of animal 

 or vegetable substances, and a simple fluid. There 

 is great reason to conclude that their germs exist, 

 not only in the air, but also in the macerating sub- 

 stances, or even in the fluid itself, and are gradually 

 unfolded according to circumstances. Among these, 

 heat and putrescence seem the most indispensable. 

 The degree of heat to which infusions may be ex- 

 posed, and still produce animalcules, is very different. 

 The smaller species still originate after infusions have 

 been subjected to 212 Fahr. in close vessels. These 

 appear to be capable of withstanding a much greater 

 degree of heat than the larger animalcules. Milk, 

 blood, urine, and other animal fluids, abound witii 

 animalcules after standing a certain time, though in 

 their natural state they do not contain them. There 

 is no certain law with regard to the particular species 

 produced by any particular infusion. In general, se- 

 veral different species will be exhibited, which dis- 

 appear, and are succeeded by others ; and sometimes 

 where there are myriads of one kind, a solitary ani- 

 malcule of a remote genus is found among them. 

 Vinegar is full of minute eels, which are also found 

 in paste. Midler conceives that the sea abounds in 

 animalcules peculiar to itself, and Spallanzani ob- 

 serves, Uiat vegetable substances dissolving in sea 

 water, produce swarms of animalcules. The minute- 

 ness of animalcules surpasses the conception of the 

 human mind. Leeuwenhoek calculates that the size 

 of some is to that of a mite, as the size of a bee to 

 that of a horse ; a hundred others will not exceed 

 Hie thickness of a single hair ; and ten thousand of a 

 different species may be contained in the space occu- 

 pied by a grain of sand. The most powerful micro- 

 scopes can only discover points in motion in the fluid, 

 gradually decreasing until they become imperceptible 

 to the view. The shape of animalcules is infinitely 

 diversified : one is a long slender line ; another is 

 coiled up like an eel or a serpent ; some are circular, 

 elliptical, or globular ; others resemble a triangle or 

 a cylinder. Some resemble thin, flat plates, and 

 some may be compared to a number of thin articulated 

 seeds. One is like a funnel ; another like a bell ; 

 others cannot be compared to any object familiar to 

 our senses. Certain animalcules, such as the protezis 

 diffluent, can change their figure at pleasure, being 

 sometimes extended to an immoderate length, at 

 other times contracted to a point. One moment they 

 are inflated to a sphere, the next completely flaccid ; 

 aiid then various eminences will project from tht- 



surface, altering them, apparently, Into animals en- 

 tirely different. Their peculiar motion is not less 

 remarkable. In several species in consists of inces- 

 sant gyration on the head as a centre, or round a 

 particular point, ns if one of the foci of an ellipse. 

 The progression of others is by means of leaps or 

 undulations ; some swim with the velocity of an ar- 

 row ; the eye can hardly follow them ; some drag 

 their Ixidies along as if with painful exertion, uiui 

 others seem to remain in perpetual resl. Their food 

 is not yet indisputably ascertained. Probably it con- 

 sists both of animal and vegetable matter; and they 

 also prey on each other. They propagate by eggs, 

 by living foetuses, and by a portion of the body be- 

 ing detadwd. Whether they have any union of 

 sexes, like the larger animals, is keenly contested. 

 The mode of the multiplication of animalcules, by 

 division into two or more parts, was first observed by 

 M. de Saussure. If one of the kinds of animalcules 

 propagating in this manner is isolated in a watch 

 glass, the traces c.f a contraction around the middle 

 of the body becomes visible, which marks incipient 

 division. The stricture soon increases insensibly, and 

 the animal then somewhat resembles a blown bladder 

 tied tight across. The contraction gradually aug- 

 ments, and the animalcule is at length changed into 

 two spherules, connected by a single point. At last 

 they separate, and two perfect animals are produced. 

 Otlier kinds divide in different manners, which we 

 have not room to describe. We will mention only 

 the volvox globator, a globular animalcule ol a green- 

 ish colour, visible by the naked eye. It is frequently 

 found in the water of ditches and marshes abounding 

 with growing vegetables, as well as those in a de- 

 composing state. Its mode of progression is by re- 

 volving on itself like a sphere ; whence its name. 

 This animalcule consists of extremely transparent 

 membranaceous substances, containing minute glo- 

 bules irregularly dispersed within it. On examination 

 with a very powerful magnifier, the globules appear 

 to be so many young volvoxes, each provided with 

 its diaphanous memorane, and within that again is 

 involved another race of descendants. Some obser- 

 vers have discovered even down to the fifth genera- 

 tion in the parent ; others have not been able to see 

 farther than the third. When the volvoxes have at- 

 tained a certain maturity, the included young begin 

 to move ; they detach themselves from the parent, 

 and successively escaping from the investing mem 

 brane, swim about. When all have left it, the com- 

 mon envelope, or mother, becomes motionless, bursts, 

 and disappears. Then the new volvoxes rapidly 

 increase in size ; their included globules J ike wise. 

 grow, they begin to move, the parent bursts, and the 

 young swim at large. By isolating these animals in 

 watch glasses, the thirteenth successive generation 

 from a single parent has been obtained. The dangers 

 to which animalcules are exposed, infinitely exceed 

 those attendent on the larger animals, not only from 

 the noxious qualities imparted to infusions, but from 

 evaporation. According to Muller, several of the 

 larger species are destroyed, and totally dissolved, 

 by simple contact with the air. Some he has seen 

 decomposed on approaching the edge of a drop ; and 

 others, amidst the rapidity of their course, have been 

 dissolved in a moment. Too much heat and cold 

 are alike fatal to them; the anguillee of vinegar, 

 however, can endure a great degree of cold. Doctor 

 Power remarks that the vinegar may be frozen and 

 thawed several times over, and they will still remain 

 as lively as ever. Some animalcules can be revived 

 after the vital functions have been suspended for a 

 long, perhaps an unlimited, time. This is the case, 

 for instance, with the wheel animal, a singular ani- 

 malcule. When the water containing this animal 



