NUTRITION 89 



been manufactured from simpler substances, artificially 

 in the laboratory, without the aid of living organisms; 

 and they may all be digested artificially in a test-tube, 

 also without the aid of living organisms; but, although 

 the attempt has often been made, no one has ever suc- 

 ceeded in artificially producing even the minutest drop 

 of living protoplasm. Only hving protoplasm, acting 

 directly on non-living matter, can bring about that 

 marvellous change. This fact is concisely expressed by 

 the Latin phrase, "Omne vivum e vivo'' (All life from life). 



87. Biogenesis. — That living matter is always descended 

 from preceding living matter, and that it never arises 

 spontaneously from the non-living is the principle of 

 biogenesis.^ Opposed to this principle is the principle 

 of ahio genesis,"^ which teaches that living matter may 

 originate from non-living without the intervention of 

 other living matter. This was formerly quite generally 

 believed. Men thought, for example, that putrid meat 

 might become transformed directly into the maggots 

 (young flies) so often found in it; but we now know that 

 maggots in decaying meat always arise from the eggs of 

 flies that have previously visited the meat and deposited 

 their eggs there. Thanks to the painstaking experiments 

 and clear thinking of Redi, Pasteur, Tyndall, and others, 

 belief in the principle of biogenesis is now practically 

 universal among scientists. 



That living matter could not, under favorable condi- 

 tions, originate from non-living matter, or that it did not 

 in the beginning, or never does now, cannot, of course, 



^ Biogenesis, from the Greek words hios {pios), life, and genesis {y^vtais) 

 generation. 



^ Abiogenesis. The prefix a (Greek alpha) deprives the remainder of 

 the word of its meaning, or reverses the meaning. 



