240 



GENERAL PHYSIOLOGY 



exactly the same in plant-cells as in Rhizopoda ; Max Schultze 

 ('63) has discussed very fully the analogy of protoplasmic move- 

 ment in the two cases. 



The amount of work that can be performed in amoeboid move- 

 ment has thus far not been ascertained, but the development of 

 energy does not appear to be considerable. 



Muscular movement is the specific form of movement of the 

 animal organism, by which apparently it is distinguished from all 

 plants. All the gross and 

 rapid mass-movements of the 

 whole animal body or of single 

 systems of organs, all those 

 remarkable movements which 

 of all vital phenomena produce 

 most the impression of living, 

 depend upon the contraction 

 of muscle-fibres. Such move- 

 ments mislead ordinary ob- 

 servers into ascribing to 

 animals a higher stage of life 

 than to the plants, the latter 

 being considered to stand 

 nearer to lifeless nature 



muc 



than to the animals. 



In contrast to amoeboid 

 protoplasmic movement, mus- 

 cular movement is especially 

 characterised by the fact that 

 its factors are co-ordinated in 

 space, in so far as the particles 

 of a muscle-fibre shift them- 

 selves in one definite direc- 

 tion. Of course it can be 

 said that in a long, straight, 

 filose pseudopodium the par- 

 ticles flow likewise in a definite 

 direction: but this direction 

 is not continual, for, in re- 

 traction the particles mingle 

 again with others and separate 

 from one another in all possible directions. In contrast to this, 

 the particles that in a muscle-fibre are the seat of contraction- 

 phenomena are constantly present as special structures in 

 the rest of the cell-protoplasm and cannot directly mix with 

 it. It is customary to term the whole muscle-cell a musclc- 

 fibre, and these specially differentiated contractile strips in it 



FIG. 99. Cell from a stamen-hair of Tradescantia 

 virginica. A, Quiet protoplasmic streaming in 

 the strands of protoplasm ; 27, the protoplasm 

 has contracted into lumps and globules at a, 6, 

 c, d. (After Kiihne.) 



