1870. J BRITISH ASSOCIATION. 327 



implicitly, or explicitly, contradicts the proposition ; and the 

 advance of science soon showed that thouQ-h Needham might be 

 quite wrong, it did not follow that Spallanzani was quite right. 



Modern Chemistry, the birth of the latter half of the eighteenth 

 century, grew apace, and soon found herself face to fiice with the 

 great problems which Biology had vainly tried to attack without 

 her help. The discovery of oxygen led to the laying of the 

 foundations of a scientific theory of respiration, and to an 

 examination of the marvellous interactions of organic substances 

 with oxygen. The presence of free oxygen appeared to be one of 

 the conditions of the existence of life, and of those sing-ular chan2;es 

 in organic matters which are known as fermentation and 

 putrefaction. The question of the generation of the infusorial 

 animacules thus passed into a new phase. For what might not 

 have happened to the organic matter of the infusions, or to 

 the oxygen of the air, in Spallanzani's experiments'? What 

 security was there that the developement of life which ought to have 

 taken place had not been checked, or prevented, by these changes ? 



The battle had to be fought again. It was needful to repeat 

 the experiments under conditions which would make sure that 

 neither the oxygen of the air, nor the composition of the organic 

 matter, was altered, in such a manner as to interfere with the 

 existence of life. 



Schulze and Schwann took up the question from this point of 

 view in 1836 and 1837. The passage of air through red-hot glass 

 tubes, or through strong sulphuric acid, does not alter the 

 proportion of its oxygen, while it must needs arrest, or destroy, any 

 organic matter which may be contained in the air. These experi- 

 menters, therefore, contrived arrangements by which the only air 

 which should come into contact with a boiled infusion should be 

 such as had either passed through red-hot tubes or through strong 

 sulphuric acid. The result which they obtained was that an infu- 

 sion so treated developed no living things, while if the same infu- 

 .sion was afterwards exposed to the air such things appeared rapidly 

 and abundantly. The accuracy of these experiments has been 

 alternately denied and affirmed. Supposing them to be accepted, 

 however, all that they really proved was, that the treatment to 

 which the air was subjected destroyed sometliing that was essen- 

 tial to the developement of life in the infusion. This " something" 

 might be gaseous, fluid, or solid; that it consisted of germs 

 remained only an hypothesis of greater or less probability. 



