Molecular Motions in Living Bodies. 



271 



tight case. It is, however, greatly accelerated and rendered 

 more energetic by heat ; and this seems to show that it is due 

 either directly to some calorical changes continually taking 

 place in the fluid, or to some obscure chemical action between 

 the solid particles and the fluid, which is indirectly promoted 

 by heat." 



The Micrographic Dictionary states " that neither light, elec- 

 tricity, magnetism, nor chemical re-agents exert any effect upon 

 it;" but it may perhaps be worth while to verify these asser- 

 tions. 



After witnessing the molecular movements with gamboge, 

 as recommended at the beginning of this paper, let two minute 

 drops, one of water and the other of gum water, be placed near 

 each other on a slide. Put a little gamboge into the water-drop, 

 and then cover both drops with a light thin piece of glass. The 

 two drops will mix slowly, and it is then easy to see the gradual 

 effect of the introduction of the gum in arresting the motion, by 

 diminishing the mobility of the fluid. To see the effects of heat, 

 place the microscope upright, lay a thin strip of sheet zinc on 

 the stage, having a little hole cut in it, and loug enough that 

 one end shall project an inch or two beyond the stop on one 

 side ; then place a piece of thin glass over the hole in the zinc, 

 put a drop of gamboge water upon it, cover with another thin 

 glass, place a spirit-lamp under the projecting part of the zinc 

 plate, and watch the result as the heat is conducted to the fluid 

 and its contents. The heat gives rise to currents in the water- 

 drop, and the additional motion thus imparted — one of distinct 

 translation in a given course — must not be confounded with 

 the peculiar molecular fidget which will go on 

 with accelerated velocity at the same time. 



Passing from instances of molecular motion 

 in water-drops, it is interesting to watch it in 

 living bodies. In the cells of confervEe it may 

 be frequently met with, and it is probably con- 

 cerned in the so-called <c swarming process " of 

 desmids and other simple plants. When the 

 chlorophyl of conferva cells is undergoing de- 

 cay, the molecular movements may be continually 

 seen ; but it is not every mode of decay that 

 breaks up the larger masses into the little 

 particles convenient for its exhibition. Fig. 1 

 represents its appearance, so far as stationary 

 dots can indicate it, in a common conferva, and 

 I have seen it conspicuously shown in the cells 

 of a moss often found in ponds — Fontinalis antvpyreUca, 



Although frequently associated with decay, it apparently 

 also forms part of the series of operations that take place in 



FIC:1. 



X 1000. 



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