on Active Molecules. 319 



observer only to the same extent as by Gleichen, and in a 

 much less degree than by MuUer, whose statements have been 

 already alluded to. 



All the observers now mentioned have confined themselves 

 to the examination of the particles of organic bodies. In 1819, 

 however, Mr Bywater, of Liverpool, published an account of 

 Microscopical Observations, in which it is stated that not only 

 organic tissues, but also inorganic substances, consist of what 

 he terms animated or irritable particles. 



A second edition of this Essay appeared in 1828, probably 

 altered in some points, but it may be supposed agreeing es- 

 sentially in its statements with the edition of 1819, which I 

 have never seen, and of the existence of which I was ignorant 

 when I published my pamphlet. 



From the edition of 1828, which I have but lately met with, 

 it appears that Mr Bywater employed a compound microscope 

 of the construction called Culpepper's, that the object was ex- 

 amined in a bright sunshine, and the light from the mirror 

 thrown so obliquely on the stage as to give a blue colour to 

 the infusion. 



The first experiment I here subjoin in his own words. 



" A small portion of flour must be placed on a slip of glass, 

 and mixed with a drop of water, then instantly applied to the 

 microscope ; and if stirred and viewed by a bright sun, as al- 

 ready described, it will appear evidently filled with innumer- 

 able small linear bodies, writhing and twisting about with ex- 

 treme activity." 



Similar bodies, and equally in motion, were obtained from 

 animal and vegetable tissues, from vegetable mould, from sand- 

 stone after being made red hot, from coal, ashes, and other 

 inorganic bodies. 



I believe that in thus stating the manner in which Mr By- 

 water's experiments were conducted, I have enabled micro- 

 scopical observers to judge of the exent and kind of optical 

 illusion to which he was liable, and of which he does not seem 

 to have been aware. I have only to add, that it is not here 

 a question of priority ; for if his observations are to be de- 

 pended on, mine must be entirely set aside. 



Juli/ 28, 1829. 



