104 THE FLOATING-MATTER OF THE AIR. 



when they are communicated to it by inoculation ; he 

 also permitted air to bubble through the liquid, and find- 

 ing no development in either case, he inferred the entire 

 absence of Bacteria and their germs from the air, con- 

 sidering water to be their exclusive habitation. Other 

 distinguished men have come to the same conclusion ; 

 while in his books and papers, and in the discussion be- 

 fore the Pathological Society already referred to. Dr. 

 Bastian has forcibly dwelt upon the result as justifying 

 the interpretation which he has affixed to his experi- 

 ments. If, he rightly urges, the air be ' entirely free ' 

 from matter which could produce Bacteria, then their 

 appearance in boiled infusions exposed to the air must 

 be due, not to anything contained in the air, but to the 

 inherent power of the infusions. Spontaneous genera- 

 tion is undoubtedly the logical outcome of the position 

 that ' the germinal matter from which Bacteria spring 

 does not exist in ordinary air.' The experiments, how- 

 ever, recorded in this memoir constitute an ocular 

 demonstration of the respective parts played by the 

 infusion and the air. A pinch of fungus-spores, taken 

 between the fingers, sown in a suitable medium, and 

 producing their appropriate crop, could not more clearly 

 indicate the origin of that crop than experiments with 

 the luminous beam indicate the origin of our harvests 

 of Bacteria. Dr. Sanderson is, I doubt not, now well 

 aware that his first statement was founded on an error of 

 interpretation. In a lecture delivered at Owens College, 

 Manchester, and published in the 'British Medical 

 Journal' for January 16, 1875, he to a great extent 

 qualifies and corrects his first inference. He there says 

 that the Bacteria ' attach themselves without doubt to 

 these minute particles, which, scarcely visible in ordinary 

 light, appear as motes in the sunbeam, or in the beam 

 of an electric lamp.' In fact the experiments on which 



