168 Mr. R. Brown on the Existence of active Molecules 



moving molecules as abundantly as those of alluvial deposits, 

 I was desirous of ascertaining whether the mobility of the 

 particles existing in organic bodies was in any degree af- 

 fected by the application of intense heat to the containing 

 substance. With this view small portions of wood, both living 

 and dead, linen, paper, cotton, wool, silk, hair, and muscular 

 fibres, were exposed to the flame of a candle or burned in 

 platina-forceps, heated by the blowpipe ; and in all these bo- 

 dies so heated, quenched in water, and immediately submitted 

 to examination, the molecules were found, and in as evident mo- 

 tion as those obtained from the same substances before burning. 

 In some of the vegetable bodies burned in this manner, in 

 addition to the simple molecules, primary combinations of 

 these were observed, consisting of fibrils having transverse 

 contractions, corresponding in number, as I conjectured, with 

 that of the molecules composing them ; and those fibrils, 

 when not consisting of a greater number than four or five 

 molecules, exhibited motion resembling in kind and vivacity 

 that of the mineral fibrils already described, while longer 

 fibrils of the same apparent diameter were at rest. . 



The substance found to yield these active fibrils in the 

 largest proportion and in the most vivid motion, was the mu- 

 cous coat interposed between the skin and muscles of the 

 haddock, especially after coagulation by heat. 



The fine powder produced on the under surface of the 

 fronds of several Ferns, particularly of Acrostichum calome- 

 lanos, and the species nearly related to it, was found to be en- 

 tirely composed of simple molecules and their primary fibre- 

 like compounds, both of them being evidently in motion. 



There are three points of great importance which I was 

 anxious to ascertain respecting these molecules, namely, their 

 form, whether they are of uniform size, and their absolute 

 magnitude. I am not, however, entirely satisfied with what I 

 have been able to determine on any of these points. 



As to form, I have stated the molecule to be spherical, and 

 this I have done with some confidence ; the apparent excep- 

 tions which occurred admitting, as it seems to me, of being 

 explained by supposing such particles to be compounds. This 

 supposition in some of the cases is indeed hardly reconcileable 

 with their apparent size, and requires for its support the further 

 admission, that, in combination, the figure of the molecule may 

 be altered. In the particles formerly considered as primary 

 combinations of molecules, a certain change of form must also 

 be allowed ; and even the simple molecule itself has sometimes 

 appeared to me when in motion to have been slightly modified 

 in this respect. 



My 



