58 THE MICROSCOPE. 



matter ; but by and by, vegetable and animal 

 life appears, and the putrifying process ceases. 

 The water becomes pure and fit for use, and so 

 continues as long as the vegetation is healthy. 

 Professor Quekett tells us, in his interesting 

 Lectures on Histology (published in 1852-4), 

 that there was before him, on his lecture-table, 

 a vessel with water, which had thus been kept 

 pure for four years, and which, he stated, would 

 still continue for any length of time in the same 

 condition, so long as that water was tenanted 

 with living plants and animalcules. 1 Shall we, 

 then, any longer despise that little roadside pool, 

 or count these microscopic plants and animals 

 useless ? We are apt to be astonished, ay, 

 disgusted, when we hear of these objects existing 

 in water. But mark the beneficence of God. 

 The plants require carbonic acid as their food, 

 and the animalcules require oxygen to keep 

 them alive. The plants obtain carbonic acid 

 from the decomposition of animal matter, and 

 again give out oxygen for animalcules. The 

 animalcule receives this oxygen, and, in return, 

 by breathing, liberates carbonic acid gas, to be 



1 Lectures on Histology, vol. ii. p. 99. 



