ANIMALCULE. 



able only by the microscope. Some have 

 supposed Uiere are others invisible. The 

 existence of these cannot well be disputed, 

 though it cannot be 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. 

 The large kinds are chiefly of the insect, 

 or vermes tribes, and of which the mono- 

 culus pulex is particularly remarkable, 

 being round sometimes in such abundance, 

 as to change the water apparently to a 

 deep red. A similar appearance is like- 

 wise occasioned by the circaria 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 hjdrachna genera, and a 

 multitude of other creatures that will be 

 noticed hereafter. 



Animalcules, microscopical The micro- 

 scope discovers legions of animalcules in 

 most liquors, as water, vinegar, beer, dew, 

 &c. 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 the ideas of infinitely 

 small bodies extremely familiar to us. A 

 naite was anciently thought the limit of 

 littleness; but we are not now surprised 

 to be told of animals twenty-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 outstrip any 

 thing greater animals are capable of! A 

 mite, how vastly faster does it run than a 

 race-horse ! M. de I'IsIr has given the 

 computation of the velocity of a little 



creature, scarcely visible by its smallncss. 

 which he found to run 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 microscopical animal- 

 cules conceals them from the human eye. 

 One of the wonders of modern 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 points ; 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 T ~3 ^ 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 __3 , that is, by the number 

 ' 



' that is > so 



P arts of 



a cubic inch is each animalcule equal to. 

 Leeuwenhoeck calculates, that athousand 

 millions of aru'malcula, 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 larger 

 than those above mentioned In the milt 

 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 var;ous 

 figures, to which vinegar is fatal ; and it 

 is known that vinegar contains animal- 

 cules in the 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 from the irritation of 

 a species of acarus, or tick, found in the 

 pustules of that ailment: when the com 



