Ixxxii REPORT — 1870. 



the fluid whicli has remained clear and desert for months, becomes, in a few 

 days, turbid and full of Ufe. 



These experiments have been repeated over and over again by independent 

 observers with entire success ; and there is one very simple mode of seeing 

 the facts for one's self, which I may as well describe. 



Prepare a solution (much used by M. Pasteur, and often called " Pasteur's 

 solution ") composed of water with tartrate of ammonia, sugar, and yeast-ash 

 dissolved therein*. Divide it into three portions in as many flasks ; boU all 

 three for a quarter of an hour; and, while the steam is passing out, stop the 

 neck of one with a large plug of cotton-wool, so that this also may be 

 thoroughly steamed. Now set the flasks aside to cool, and when their 

 contents are cold, add to one of the open ones a drop of filtered infusion of 

 hay which has stood for twenty-four hours, and is consequently full of the 

 active and excessively minute organisms known as Bactei-ia. In a couple of 

 days of ordinary warm weather, the contents of this flask will be milky, 

 from the enormous multiplication of Bacteria. The other flask, open and 

 exposed to the air, will, sooner or later, become milky with Bacteria, and 

 patches of mould may appear in it ; while the liquid in the flask, the 

 neck of which is plugged with cotton-wool, wUl remain clear for an inde- 

 finite time. I have sought in vain for any explanation of these facts, 

 except the obvious one, that the air contains germs, competent to give rise to 

 Bacteria, such as those with which the first solution has been knowingly and 

 purposely inoculated, and to the mould Funr/i. And I have not yet been 

 able to meet with any advocate of Abiogenesis who seriously maintains that 

 the atoms of sugar, tartrate of ammonia, yeast-ash, and water, under no 

 influence but that of free access of air and the ordinary temperature, rear- 

 range themselves and give rise to the protoplasm of Bacterium. But the 

 alternative is to admit that these Bacteria arise from germs in the air ; and if 

 they are thus propagated, the burden of proof, that other like forms are gene- 

 rated in a different manner, must rest with the assertor of that proposition. 



To sum up the effect of this long chain of evidence : — 



It is demonstrable, that a fluid eminently fit for the development of the 

 lowest forms of life, but which contains neither germs nor any protein com- 

 pound, gives rise to living things in great abundance if it is exposed to 

 ordinary air ; while no such development takes place if the air with which 

 it is in contact is mechanically freed from the solid particles, which ordinarily 

 float in it and which may be made visible by appropriate means. 



It is demonstrable, that the great majority of these particles are de- 

 structible by heat, and that some of them are germs, or living particles, 

 capable of giving rise to the same forms of life as those which appear when 

 the fluid is exposed to unpurified air. 



It is demonstrable, that inoculation of the experimental fluid with a drop 

 of hquid known to contain living particles gives rise to the same phenomena 

 as exposure to unpurified au\ 



And it is fiuther certain that these living particles are so minute that the 

 assumption of their suspension in ordinary air presents not the slightest 

 difficulty. On the contrary, considering their lightness and the wide 

 diftusion of the organisms which produce them, it is impossible to conceive 

 that they should not be suspended in the atmosphere in myriads. 



Thus the evidence, direct and indirect, in favour of Biogenesis for aU 

 known forms of life must, I think, be admitted to be of great weight. 



* Infusion of hay, treated in the same way, yiekls similar results ; but as it contains 

 organic matter, the argument which follows cannot be based upon it. 



