84 THE POPULAR SCIENCE MONTHLY. 



Thus when the Nile from Pharian fields is fled, 

 And seeks, with ebbing tide, his ancient bed, 

 The fat manure with heavenly fire is warmed, 

 And crusted creatures, as in wombs, are formed ; 

 These, when they turn the glebe, the peasants find; 

 Some rude, and yet unfinished in their kind. 

 Short of their limbs, a lame, imperfect birth ; 

 One half alive, and one of lifeless earth." 



Crude ideas of this kind prevailed universally until the seventeenth 

 century. The celebrated physiologist, Dr. William Harvey, the dis- 

 coverer of the circulation of the blood, has the credit of first propound- 

 ing the modern view expressed in the maxim " Omne vivum ex vivo," 

 which being interpreted signifies, " No life without antecedent life." 

 He maintained that all living beings proceed from eggs ; but exactly 

 what he meant by " eggs," that is, whether they were always derived 

 from parental organisms, or might originate in some other way, is con- 

 sidered uncertain. 



The first distinct announcement of the doctrine that all living matter 

 has sprung from preexisting living matter, was made by Francesco 

 Redi, an Italian physician, who published his views just two hundred 

 and four years ago. His position is thus stated by Prof. Huxley : 

 " Here are dead animals, or pieces of meat ; I expose them to the 

 air in hot weather, and in a few days they swarm with maggots. 

 You tell me that these are generated in the dead flesh ; but, if I put 

 similar bodies, while quite fresh, into ajar, and tie some fine gauze over 

 the top of the jar, not a maggot makes its appearance, while the dead 

 substances, nevertheless, putrefy just in the same way as before. It is 

 obvious, therefore, that the maggots are not generated by the corrup- 

 tion of the meat, and that the cause of their formation must be a some- 

 thing which is kept away by gauze. But gauze will not keep away 

 aeriform bodies or fluids. This something must, therefore, exist in the 

 form of solid particles too big to get through the gauze. Nor is one 

 left long in doubt what these solid particles are ; for the blow-flies, at- 

 tracted by the odor of the meat, swarm round the vessel, and urged by 

 a powerful but in this case misleading instinct, lay eggs out of which 

 maggots are immediately hatched upon the gauze. The conclusion, 

 therefore, is unavoidable : the maggots are not generated by the meat, 

 but the eggs which give rise to them are brought through the air by 

 the flies." 



These experiments were unanswerable ; but the doctrine of sponta- 

 neous generation had been too long and firmly believed, to be surren- 

 dered merely because of the demonstrated falsity of its grounds. It 

 was held to have the sanction of the Bible, which affirmed that bees 

 were generated from the carcass of a dead lion : Dr. Redi was there- 

 fore called upon to defend himself against the charge of impugning 

 Scripture authority. 



