IN THE LAST HALF-CENTURY. 119 



the supposed evidence of abiogenesis was 

 untrustworthy. 



During the present epoch, the ques- 

 tion, whether living matter can be pro- 

 duced in any other way than by the phys- 

 iological activity of other living matter, 

 has been discussed afresh with great 

 vigor ; and the problem has been investi- 

 gated by experimental methods of a pre- 

 cision and refinement unknown to previ- 

 ous investigators. The result is that the 

 evidence in favor of abiogenesis has ut- 

 terly broken down, in every case which 

 has been properly tested. So far as the 

 lowest and minutest organisms are con- 

 cerned, it has been proved that they 

 never make their appearance, if those pre- 

 cautions by which their germs are cer- 

 tainly excluded are taken. And, in re- 

 gard to parasites, every case which seemed 

 to make for their generation from the 

 substance of the animal, or plant, which 

 they infest has been proved to have a to- 



