130 <>X THi: PHYSICAL BASIS OF LIFE ni 



times trains of granules may be seen coursing 

 swiftly in opposite directions within a twenty- 

 thousandth of an inch of one another; while, 

 occasionally, opposite streams come into direct 

 collision, and, after a longer or shorter- struggle, 

 one predominates. The cause of these currents 

 seems to lie in contractions of the protoplasm 

 which bounds the channels in which they flow, 

 but which are so minute that the best microscopes 

 show only their effects, and not themselves. 



The spectacle afforded by the wonderful energies 

 prisoned within the compass of the microscopic 

 hair of a plant, which we commonly regard 

 merely passive organism, is not easily forgotten 

 by one who has watched its display, continued 

 hour after hour, without pause or sign of weaken- 

 ing. The possible complexity of many other 

 organic forms, seemingly as simple as the proto- 

 plasm of the nettle, dawns upon one ; and the 

 comparison of such a protoplasm to a body with 

 an internal circulation, which has been put forward 

 by an eminent physiologist, loses much of its start- 

 ling character. Currents similar to those of the hairs 

 of the nettle have been observed in a great multi- 

 tude of very different plants, and weighty authori- 

 ties have suggested that they probably ocvur. in 

 more or less perfection, in all young vegetable 

 edls. If such be the case, the wonderful noonday 

 silence of a tropical forest is, after all, due only to 

 the dulness of our hearing; and could our ears 



