48 BENNETT, ON THE MOLECULAR THEORY. 



aucl by sudden section of the nerve going to the skin, 

 M'hile darkness and irritation of the nerve or skin causes 

 diffusion. Sudden amputation of a limb produced, at first, 

 by diffusion, followed by the concentration of death. These 

 movements of the pigment-molecules are peculiarly vital, 

 and altogether independent of the cell-wall or nucleus. The 

 cell-wall is stationary, and acts only as a sac or investing 

 membrane around the moving particles, while the concen- 

 tration of these about the nucleus is purely accidental, and 

 frequently occurs in other parts of the cell. The author had 

 seen these molecules himself, as Mr. Lister describes tliem, 

 streaming out to and returning from the circumference under 

 the influence of the stimuli referred to, where no cell nor 

 nuclear action could be thought of. 



.5th. There are many other kinds of movements which are 

 evidently independent of cells, for example, those of cilia 

 and of spermatozoids. The former are outside cells, and the 

 latter only move when they are liberated from cells. The 

 contractile fibrillse of muscle are evidently not dependent for 

 their inherent power on cells or other form of structure, but 

 on the square-shaped molecules of which its substance is 

 composed. All these phenomena, therefore, are connected 

 with the molecules themselves; the force occasioning them 

 is a molecular force, and has nothing to do with pre- 

 existing cells, or supposed germinal centres, as some have 

 imagined. 



Again, the power of combination between these molecules, 

 which, under peculiar conditions, not only move but so 

 move as to advance towards and press upon each other that 

 they at length unite and produce higher forms, must also 

 be attributed to a molecular force operating in obedience to 

 fixed laws. Thus, it was demonstrated by Newton that in a 

 sphere the total attraction resulting from the particular 

 attraction of all its component parts is, as regards any body 

 draAvn towards it, the same as. if they had been concentrated 

 at the centre. Hence minute spherical particles, as so many 

 gravitating points, will be drawn towards each other with a 

 force varying inversely as the squares of the distances between 

 their respective centres. The author referred at length to 

 the able descriptions of Mr. Rainey,* as to the physical laws 

 regulating the formation and disintegration of bodies by 

 molecular attraction and repulsion, as well as to the effects 

 of molecular superposition, showing that the same physical 

 power which leads to the formation of these artificial bodies, 

 when long continued, causes their disintegration and destruc- 

 * Op. cit. See also papers in the ' Microscopical Journal,' 1860. 



