354 Prof. J. Tyndall on Ferments and Germs. [June 21, 



themselves. Germs have given place to things which are ultramicro- 

 scopical — to molecular aggregates — of which all we can say is, what we 

 have already said about the ferments, that they occupy the border-land 

 between living and non-living things." 



As directed against " germs " the argument that the " germinal matter" 

 is capable of resisting destructive influences which are fatal to the Bacteria 

 themselves, will, I think, be found on consideration to lack validity. 

 Nobody is better acquainted than Dr. Sanderson with the two forms under 

 which the contagium of splenic fever appears. He knows that the one is 

 fugitive and readily destroyed, the other persistent and destroyed with 

 difficulty. Now the recent researches of Koch, which have been verified 

 by Cohn, prove conclusively that the difference here referred to is based 

 upon the fact that the fugitive contagium is the developed organism of 

 Bacillus anthracis, while the persistent contagium is the spore of that 

 organism. Dallinger's excellent observations also establish a difference 

 between the death-temperatures of monad germs and of adult monads ; 

 while I need not do more than refer to the forthcoming Part of the 

 Philosophical Transactions for illustrations of the extraordiuary dif- 

 ferences of the same nature which my recent researches have brought 

 to light. 



Dr. Sanderson credits me with " admitting" that the germinal or life- 

 producing matter out of which Bacteria originate exhibits no structural 

 characters which can be appreciated by the microscope. Not only do I 

 admit it, but I made it a special object of my lecture before the British 

 Association at Liverpool in 1870*, to show how inappropriate it is to 

 invoke the microscope in deciding questions of ultimate structure. After 

 experimentally demonstrating the existence of a world of particles far 

 beyond the reach of the microscope, I thus express myself : — 



" Many of our physiological observers appear to form a very inadequate 

 estimate of the distance which separates the microscopic from the mole- 

 cular limit, and often employ a phraseology calculated to mislead. When, 

 for example, the contents of a cell are described, without qualification, as 

 ' perfectly homogeneous,' or as ' absolutely structureless,' because the 

 microscope fails to distinguish any structure, or when two structures are 

 pronounced to be ' without difference ' because the microscope can detect 

 none, then I think the microscope begins to play a mischievous part. 



" A little consideration will make it plain that the microscope can have 

 no voice in the question of ultimate germ-structure. What is it that 

 causes water to contract at 39° P., and to expand until it freezes ? It is 

 a structural process of which the microscope can take no note ; nor 

 is it likely to do so by any conceivable extension of its powers. When 

 distilled water is placed in the field of an electro- magnet, will any change 

 be observed by a microscope when the magnet is excited ? Absolutely 

 none ; and still profound and complex changes have occurred. Pirst of 

 * 1 Fragments of Science,' 5th edition, pp. 447, 448. 



