92 The Conditions of Infusorial Life. 



created beings, other beings similar to themselves, while in putri- 

 factive substances it produces only microscopic animalcules ." 

 It will at once occur to every reader, that although the germs of 

 the larger infusoria might be excluded with moderate precau- 

 tions, those of the smaller kinds, which must be extremely minute 

 objects under the highest powers of magnification our micro- 

 scopes possess, would, if widely disseminated, be so difficult to 

 keep out of any large and complicated piece of apparatus, as 

 to justify doubts in the accuracy of any series of experiments 

 leading to a conclusion demanding unusual severity of proof. 

 And even the successful repetition of any set of experiments, 

 which appear to support a theory at variance with the general 

 conclusions of science, ought not to command our assent unless 

 other modes of testing the question afforded the same results. 

 It would also be reasonable to give greater weight to the 

 simplest methods, if complete in themselves, as offering fewer 

 chances of error, than trials made with more complicated appa- 

 ratus, and presenting a greater variety of parts. Following 

 this rule, it is no disparagement to M. Pouchet/s qualifications as 

 a manipulator if we accept his experiments for their general in- 

 formation, and at the same time reject their conclusiveness for 

 the particular end he had in view. In this spirit we may cite 

 several of his illustrations without recurring to the generation 

 arguments at every step. 



Under the head of " Eliminations of the Putrescible Body/' 

 we find that maize, peas, haricots, and lentils, were separately" 

 burnt in an iron ladle at a red heat, and their remains placed 

 in distinct vessels with distilled water, and covered with 

 separate bell-glasses. In twenty days of warm temperature, the 

 maize vessel exhibited an abundance of a fungus (Aspergillus) , 

 but no animalcules, nor did any appear till another fifteen days 

 had expired ; the peas yielded numerous and varied microzoaries, 

 and especially Monas attenuate/,. The lentils did the same, 

 and the beans a still thicker population of the same monads. 

 tc Criterium " vessels, with the same seeds not burnt, produced 

 abundance of animalcules in three days, and of a higher grade 

 than in the former cases. Here we see the influence of minute 

 variations in the chemical composition of the several incinera- 

 tions, and possibly also of their mechanical condition, in offering 

 appropriate circumstances for the evolution of different germs. 



In another experiment, some hay was heated to 200° to 210 o 

 centigrade, and even a little higher, till it began to burn, and it 

 was then immersed in distilled water, covered with a plate of 

 glass, and put under a shade. After four days of warmth, the 

 infusions contained a quantity of dead vibrions, with a large 

 population of Glaucoma scintillans and minute monads. From 

 these and similar experiments, it is plain that the production 



