140 MEN-UTE ORGANISMS. 



long known tliat tlie atmospheric dust transported by every wind 

 and deposited by every caLn is full of microscopic life or of its 

 relics. The soil on which the city of Berhn stands, contains, at 

 the depth of ten or fifteen feet below the surface, living elabo rat- 

 ers of silex ; * and a microscopic examination of a handful of 

 earth connected with the material evidences of guilt has enabled 

 the naturalist to point out the very spot where a crime was com- 

 mitted. It has been computed that one-sixth part of the solid 

 matter let faU by great rivers at their outlets consists of still rec- 

 ognizable infusory shells and shields ; and, as the friction of roll- 

 ing water must reduce many of these fragile structures to a state 

 of comminution which even the microscope can not resolve into 

 distinct particles, and thus identify as relics of animal or of vege- 

 table life, we must conclude that a considerably larger proportion 

 of river deposits is really the product of animalcules.f 



It is evident that the chemical, and in many .cases the mechan- 

 ical, character of a great number of the objects important in the 

 material economy of human life, must be affected by the presence 

 of 80 large an organic element in their substance, and it is equally 

 obvious that all agricultural and all industrial operations tend to 

 disturb the natural arrangements of this element, to increase or 

 to diminish the special adaptation of every medium in which it 

 lives to the particular orders of beiQg inhabited by it. The con- 

 version of woodland into pasturage, of pasture into plough-land, 

 of swamp or of shallow sea into dry ground, the rotations of 

 cultivated crops, must prove fatal to milKons of living things 

 upon every rood of surface thus deranged by man, and must, at 

 the same time, more or less fully compensate this destruction of 



* WiTTWER, Physikalische Qeographie, p. 143. 



f To vary the phrase, I make occasional use of animalcule, which, as a popu- 

 lar designation, embraces all microscopic organisms. The name is founded 

 on the now exploded supposition that all of them are animated, which was the 

 general belief of naturalists when attention was first drawn to them. It was 

 soon discovered that many of them were unquestionably vegetable, and there 

 are numerous genera the true classification of which is matter of dispute 

 among the ablest observers. There are cases in which objects formerly taken 

 for living animalcules turn out to be products of the decomposition of matter 

 once animated, and it is admitted that neither spontaneous motion nor even 

 apparent irritability are sure signs of animal life. 



