60 MOLECULAR MOTION. [CHAP. n. 



apparently irregular and oscillating. Those of the former kind are 

 familiarly known in the vegetable kingdom by the Cyclosis which 

 takes place in the oblong cells of Chara; the granules, which may 

 be seen in motion, are quite passive and are carried along by 

 currents within the cell. Motions of the latter kind have been 

 seen by Schwann among the granules contained in the cells of the 

 germinal membrane of the hen's egg, as if occasioned by an en- 

 dosmotic current through the wall of the cell. This membrane is 

 the seat of active change, the development and growth of new 

 cells, destined for the evolution of the textures of the embryo ; and 

 they derive their nutriment from the yolk, on the surface of which 

 they lie. Here the contained particles are passive, and the motion 

 in them is only the index of the currents which give rise to it. A 

 molecular motion of the same kind may be seen in the very minute 

 granules, which occupy the cells of the membrane of black pigment 

 on the choroid coat of the eye. Whether this go on during life, it 

 is, of course, impossible to say, but the conditions for its production 

 are undoubtedly present. In the blood may be seen another ex- 

 ample of the kind of motion under consideration. The circulation 

 of this fluid may be readily followed in transparent parts ; and 

 certain particles, the blood-discs, which float in it in great numbers, 

 exhibit movements which can scarcely be attributed solely to the 

 current of the circulating fluid. It is probable that secondary 

 currents may be established in the blood, or that attractions and 

 repulsions may exist between the particles themselves, or between 

 them and the walls of the blood-vessels giving rise to these motions. 

 According to some observers, the blood-discs undergo actual changes 

 of shape, becoming now swollen, and now flattened ; and this 

 might be attributed to the alternate predominance of endosmose 

 or exosmose. But the statement, that they possess an inherent 

 power of contraction of their own, stands greatly in need of con- 

 firmation. 



Organic Molecular Action occurs in nearly all the internal pro- 

 cesses. The introduction of new matter from without into the 

 blood ; the removal of effete particles by a process of absorption ; 

 the transfer of nutrient matter from the blood to supply the place 

 of the particles thus removed ; the separation of organic compounds 

 in glands, cannot take place without a movement of molecules in 

 the textures concerned in these processes. We are as much at 

 liberty to infer, that these motions are produced by certain affinities 

 of the particles of the tissues, as that chemical action is the result 

 of affinities between certain forms of matter. These motions of the 



