ON MICROSCOPIC DISCOVERY. 



623 



aided eye of man cannot detect, and the most 

 colossal animated structure that walks the 

 globe. An examination into the minute has 

 a manifest tendency to strengthen belief in 

 an universal and particular Providence, and 

 affords a striking comment on the declaration 

 of Holy Writ, that "not a sparrow falleth to 

 the ground without the knowledge of our 

 heavenly Father." 



CHAP. II. 



INFUSORIAL, ANIMALCULES. 



THE elaborate examinations that have re- 

 cently been made regarding infusorial ani- 

 malcules have brought vast accessions to our 

 knowledge of animated nature. Of these 

 atomic germs of vitality, little had been pre- 

 viously discovered beyond the fact of their 

 existence ; and indeed, many species, on ac- 

 count of their extreme minuteness, and the 

 vast amplifying power necessary for their 

 developement, hdd not till very recently been 

 observed at all. It is not however to their 

 mere existence that the microscopist now calls 

 attention, but to all the details of their exter- 

 nal form and internal structure ; to their habits, 

 modes of action, natural instincts, and to all 

 the economy of their being. The mind is 

 overwhelmed and confounded whilst we read 

 (as Mr Pritchard, in his Natural History of 

 Animalcules, has enabled us to do) of the 

 organization and vital properties of a living 

 atom, so inconceivably minute, that five hun- 

 dred millions of them in a mass, would present 

 little more than a sensible point to the un- 

 assisted eye. Such an announcement will be 

 met by much scepticism ; and scepticism, in this 

 instance, is indeed pardonable ; for with the 

 object before him, the observer can scarcely 

 yield his belief, whilst mathematical truth 

 and actual observation are attesting the fact. 



The term infusorial is applied to the various 

 species of animalcules discovered in vegetable 

 and animal infusions. They exist naturally 

 in all stagnant waters, wherein vegetable or 

 animal matter is decomposing ; and (hey can 

 be produced artificially by making an infusion 

 of vegetable substances, and suffering it to 

 stand till it has fermented, and become in 

 some degree putrid. The most rational and 

 philosophical way of accounting for the pre- 

 sence of animalcules in infusions, is to adopt 

 the hypothesis that the atmosphere is teeming 

 with minute germs of animal and vegetable 

 life, that they form part of every thing we 

 taste or touch, but that, for their perfect 

 development, a suitable nidus is necessary, 

 which nidus is presented in an infusion of 



some kind or other. These animalcular ova, 

 it would appear, depend much for the form 

 they are to assume when evolved, upon the 

 peculiar nidus in which they are deposited ; 

 for the same infusion, in different stages of 

 fermentation and putrescence, developes dif- 

 ferent species of animalcules. Or, perhaps, 

 the ova themselves have distinct characters, 

 and the infusion may become successively 

 adapted for the developement of the various 

 species. Leaving this point as one of mere 

 conjecture, we pass on to observe that optical 

 science has rendered these animalcules legiti- 

 mate subjects of natural history : and we are 

 consequently to acquaint ourselves, as before 

 observed, not only with their extreme little- 

 ness, but with all the peculiarities that consti- 

 tute their generic and special differences. 



Before entering upon a particular descrip- 

 tion of the various kinds of animalcules found 

 in infusions, we shall lay before the reader 

 Mr Pritchard 's lucid and perspicuous sum- 

 mary of their peculiarities. 



" The term animalcule, which implies 

 nothing more than the diminutive of animal, 

 has been commonly used to denote those living 

 creatures inhabiting fluids, which are too 

 minute to be scanned, or even seen by the 

 naked eye : such, for instance, as those pro- 

 duced in inconceivable numbers from infusions 

 of animal and vegetable matter : it compre- 

 hends as well such as are found in, and are 

 peculiar to, the bodies of larger animals : this 

 latter class, however, does not fall within our 

 province. 



" In the variety of systems that have been 

 put forth respecting these creatures, the 

 main characteristics of each have referred 

 either to a difference in their size, or to the 

 general appearance of their external forms : 

 the present design, however, is not to inves- 

 tigate the value of these. Until the introduc- 

 tion of vegetable colouring matter into the 

 fluid which supplies them with food an ex- 

 periment that has been attended with very 

 successful results these creatures were com- 

 monly supposed to be entirely devoid of in- 

 ternal organization, and to be nourished by the 

 simple process of cuticular absorption. By 

 the application of coloured substances, which, 

 moreover, have been found to invigorate rather 

 than to depress the animalcule, and to main- 

 tain it in the full exercise of all its functions, 

 this erroneous notion is set at rest, and an 

 internal structure is discerned in some, equal 

 to, if not surpassing that of the larger inver- 

 tebrated animals, and comprising a muscular, 

 nervous, and, in all probability, vascular 

 system ; all wonderfully contrived for the per- 

 formance of their respective offices. 



" The most obvious portion of their in- 

 ternal structure is undoubtedly that connected 



