BIOLOGY 



PROFESSOR HUXLEY'S ADDRESS. 



AT the meeting of the British Association, Professor Huxley, 

 after presenting a long series of facts bearing upon the germ the- 

 ory, continued : 



"To sum up the effect of this long chain of evidence, it is dem- 

 onstrable that a fluid eminently fit for the development of the 

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

 tean compound, 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 destructible 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 uflpurified aiu. It is demonstrable that inoc- 

 ulation of the experimental fluid with a drop of liquid known to 

 contain living particles gives rise to the same phenomena as expos- 

 ure to unpuriiied air. And it is further certain that these living par- 

 ticles are so minute that the assumption of their suspension in ordi- 

 nary air presents not the slightest difficulty. On the contrary, con- 

 sidering their lightness and the wide diffusion of the organisms 

 which produce them, it is impossible to conceive that they should 

 not be suspended in the atmosphere in myriads. Thus, the evi- 

 dence, direct and indirect, in favor of biogenesis for all known 

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

 On the other side, the sole assertions worthy of attention are, that 

 hermetically sealed fluids, which have been exposed to great and 

 long-continued heat, have sometimes exhibited living forms of 

 low organization when they have been opened. The first reply 

 that suggests itself is the probability that there must be some 

 error about these experiments, because they are performed on an 

 enormous scale every day, with quite contrary results. Meat, 

 fruit, vegetables, the very materials of the most fermentable and 

 putresdble infusions, are preserved to the extent, I suppose I may 

 say, of thousands of tons every year, by a method which is a 

 mere application of Spellanzani's experiment. The matters to 

 be preserved are well boiled in a tin case provided with a small 

 hole, and this hole is soldered up when all the air in the case has 



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