Mr. Brown's Additional Remarks on Active Molecules. 165 



with when I printed the account of my Observations, the au- 

 thor gives an account of the very remarkable motions of the 

 spicula which form the silvery part of the choroid coat of the 

 eyes of fishes. 



These spicula were examined with a simple microscope, and 

 as opake objects, a strong light being thrown upon the drop 

 of water in which they were suspended. The appearances are 

 minutely described, and very ingenious reasoning employed 

 to show that, to account for the motions, the least improbable 

 conjecture is to suppose the spicula animated. 



As these bodies were seen by reflected and not by trans- 

 mitted light, a very correct idea of their actual motions could 

 hardly be obtained; and with the low magnifying powei's 

 necessarily employed with the instrument and in the man- 

 ner described, the more minute nearly spherical particles or 

 active Molecules which, when higher powers were used, I 

 have always found in abundance along with the spicula, en- 

 tirely escaped observation. 



Dr. Drummond's researches were strictly limited to the 

 spicula of the eyes and scales of fishes ; and as he does not 

 appear to have suspected that particles having analogous mo- 

 tions might exist in other organized bodies, and far less in 

 inorganic matter, I consider myself anticipated by this acute 

 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. By water, 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 micro- 

 scope of the construction called Culpepper's, that the object 

 was examined in a bright sunshine, and the light from the 

 mirror thrown so oblicjuely on the stage as to give a blue 

 colour to the infusion. 



The first cx])criincnt 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; 



