ON THE PHYSICAL BASIS OF LIFE 99 



successive stalks of corn by a breeze produces the ap- 

 parent billows of a cornfield. 



But, in addition to these movements, and independ- 

 ently of them, the granules are driven, in relatively 

 rapid streams, through channels in the protoplasm 

 which seem to have a considerable amount of persist- 

 ence. Most commonly, the currents in adjacent parts 

 of the protoplasm take similar directions; and, thus, 

 there is a general stream up one side of the hair and 

 down the other. But this does not prevent the existence 

 of partial currents which take different routes; and 

 sometimes trains of granules may be seen coursing 

 swiftly in opposite directions within a twenty-thou- 

 sandth 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 mi- 

 croscopes 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 as a merely passive 

 organism, is not easily forgotten by one who has 

 watched its display, continued hour after hour, without 

 pause or sign of weakening. The possible complexity 

 of many other organic forms, seemingly as simple as the 

 protoplasm of the nettle, dawns upon one; and the 

 comparison of such a protoplasm to a body w T ith an in- 

 ternal circulation, which has been put forward by an 

 eminent physiologist, loses much of its startling charac- 

 ter. Currents similar to those of the hairs of the nettle 

 have been observed in a great multitude of very differ- 

 ent plants, and weighty authorities have suggested that 



