26 LIVING MATTER OR PROTOPLASM. 



Protoplasm in Action. We know that living things are the 

 seat of active changes, which taken together constitute their life. 

 In the last analysis these changes are undoubtedly chemical 

 actions taking place in the protoplasm, which in many cases do 

 not produce visible results, but only molecular transformations. 

 There is no doubt that extensive and probably very complex 

 molecular actions go on in the protoplasm of young growing 

 cells, though it may appear absolutely quiescent to the eye, even 

 when this is armed with a powerful microscope. In other cases, 

 the chemical action produces perceptible changes in the proto- 

 plasm, for instance, some form of motion, just as the invisible 

 chemical action in an electrical battery may be made to produce 

 visible effects (light, locomotion, etc.) through the agency of an 

 electrical motor. 



A familiar instance of protoplasmic movement is the contrac- 

 tion of a muscle. This process is most likely a change of molec- 

 ular arrangement, causing the muscle, while keeping its exact 

 bulk, to change its form, the two ends being brought nearer 

 together (Fig. 14). The visible change of form is here supposed 

 to be due to an invisible change of molecular arrangement, and 

 this in turn to be produced by chemical action taking place in the 

 living substance. 



A striking and beautiful example of movement in protoplasm 

 occurs in the simple organism known as Amoeba (Fig. 15). The 

 entire body of this animal consists of a mass of naked protoplasm 

 enclosing a nucleus, or sometimes two; in other words, it is a 

 single naked cell. The protoplasm of an active Amoeba is in a 

 state of ceaseless movement, contracting, expanding, flowing, and 

 changing the form of the animal to such an extent that it is known 

 as the " Proteus animalcule." The whole movement is a kind of 

 mix. A portion of the protoplasm flows out from the mass, 

 making one or more prolongations ( psendc^ods] into which the 

 remainder of the protoplasm finally passes, so that the whole 

 body advances in the direction of the flow. If particles of food 

 be met with, the protoplasm flows around them, and when they 

 have been digested within the body, the protoplasm flows on- 

 ward, leaving the refuse behind. Hour after hour and day after 

 day this flowing may go on, and there is perhaps no more fasci- 

 nating and suggestive spectacle known to the biologist. A simi- 

 lar change of form is exhibited by the colorless corpuscles of 



