Biology 677 



At the present day, when the conditions must be very differ- 

 ent from those which could have existed when life was first 

 evolved, there does not seem to be any spontaneous transforma- 

 tion of lifeless into living matter. This has only been proved in 

 quite recent years; the doctrine of spontaneous generation has 

 been held by all primitive peoples, and maintained itself even 

 among scientific men, until the middle of last century. The popu- 

 lar belief that a dead carcase would breed bees is to be found in 

 the Bible and in Virgil. Country-folk believe to this day that a 

 horsehair put into a pond will become transformed into an eel; 

 and it was only in the eighteenth century that Redi disproved the 

 popular supposition that maggots were "bred" from decaying 

 meat, by showing that none appeared when the meat was screened, 

 and when the flies could not, therefore, lay their eggs on it. 



The discovery of the microscope, however, and its revelation 

 of the teeming, hitherto invisible world of protozoa, unicellular 

 plants, moulds, and bacteria, altered the position; and it was be- 

 lieved almost universally that these low forms of life were gener- 

 ated spontaneously in the processes of decay. It was Pasteur, 

 the great French scientist, who, together with Tyndall and others 

 finally gave the theory of spontaneous generation its death-blow. 

 By a series of ingenious experiments, he showed that liquids, 

 which in ordinary circumstances would become a mass of bacteria 

 in a day or so, remained free from all living organisms if 

 thoroughly boiled. This was true even if fresh air was admitted 

 to them, provided that it was filtered through cotton-wool, or in 

 some way first made to deposit any solid particles it contained. 

 In fact, he showed conclusively that whenever life appeared 

 "spontaneously" in a culture-fluid, it had always really been trans- 

 ported there through the air in the form of invisible "germs," and 

 thus, without realising it, he laid the foundations of the whole 

 science and practice of bacteriology. Nowhere is there to be found 

 a better example of vastly important practical results accruing 

 from the simple pursuit of knowledge for knowledge's own sake. 



VOL. Ill 8 



