FOSSIL ANIMALCULES. 



measures only the 12000th of an inch. It follows from these 

 dimensions that in a drop of human blood which would remain 

 suspended from the point of a fine needle, there must be about 

 3,000000 of discs, and' in a like drop of the blood of the musk- 

 deer, there would be about 120,000000 ; yet these corpuscles are 

 rendered not only distinctly visible to the senses by the aid of 

 the microscope, but their forms and dimensions are rendered 

 apparent. 



21. But these globules, small as they are, are exceeded in 

 minuteness by innumerable creatures, whose existence the micros- 

 cope has disclosed, and whose entire bodies are inferior in magni- 

 tude to the globules of blood. 



Microscopic research has disclosed the existence of animals, a 

 million of which do not exceed the bulk of a grain of sand, and 

 yet each of these is composed of members as admirably suited to 

 their mode of life as those of the largest species. Their motions 

 display all the phenomena of vitality, sense, and instinct. In the 

 liquids which they inhabit they are observed to move with the 

 most surprising speed and agility; nor are their motions and 

 actions blind and fortuitous, but evidently governed by choice 

 and directed to an end. They use food and drink, by which they 

 are nourished, and must, therefore, be supplied with a digestive 

 apparatus. They exhibit a muscular power far exceeding in 

 strength and flexibility, relatively speaking, the larger species. 

 They are susceptible of the same appetites, and obnoxious to the 

 same passions, as the superior animals, and, though differing in 

 degree, the satisfaction of these desires is attended with the same 

 results as in our own species. 



Spallanzani observes that certain animalcules devour others so 

 voraciously that they fatten and become indolent and sluggish by 

 over-feeding. After a meal of this kind, if they be confined in 

 distilled water so as to be deprived of all food, their condition 

 becomes reduced, they regain their spirit and activity, and once 

 more amuse themselves in pursuit of the more minute animals 

 which are supplied to them. These they swallow without depriving 

 them of life, as by the aid of the microscope, the smaller, thus 

 devoured, has been observed moving within the body of the 

 greater. 



An animalcule called a Rotifer is represented magnified in an 

 enormous proportion in fig. 3, page 193. This creature has the 

 appearance of throwing out before it two toothed wheels, which, 

 being moved with prodigious velocity, produce whirlpools in the 

 fluid in which it moves, into which other still smaller animalcules 

 are drawn. This apparent apparatus of helical wheels, like those 

 which propel the recently constructed steam-vessels, is supposed 



201 



