Mr Brown on Active Molecules. 45 



adds, they 'lavc been confounded by some very respectable ob- 

 servers. 



In 1814, Dr James Drummond of Belfast, published, in the 

 7th volume of the Transactions of the Royal Society of Edin- 

 burgh, a valuable paper, entitled " On certain appearances ob- 

 served in the Dissection of the Eyes of Fishes.'" 



In this Essay, which I regret I was entirely unacquainted 

 with when I printed the account of my observations, the author 

 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 mi- 

 nutely 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 transmit- 

 ted light, a very correct idea of their actual motions could hardly 

 be obtained ; and with the low magnifying powers necessarily- 

 employed with the instrument and in the manner described, the 

 more minute nearly spherical particles or active molecules which, 

 when higher powers were used, I have always found in abun- 

 dance along with the spicula, entirely escaped observation. 



Dr Drummond's researches were strictly limited to the spi- 

 cula of the eyes and scales of fishes ; and as he does not appear 

 to have su.spected that particles having analogous motions mio-ht 

 exist in other organized bodies, and far less in inorganic mat- 

 ter, 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, how- 

 ever, Mr By water, of Liverpool, published an accoimt of Micro- 

 scopical Observations, in which it is stated that not only organic 

 tissues, but also inorganic substances, consist of what ho 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 essen- 



