CHAPTER IV 



THEORETICAL AND GENERAL 



SECTION 45. The supposed Analogy between the Shock -stoppage of 

 Streaming and a Muscular Contraction. 



HoRMANN (1. c.) considers that the shock-stoppage of streaming 

 corresponds to an ordinary muscular contraction, and that the different 

 response is due to the different structure of the motor-mechanisms in the 

 two cases. In support of this conclusion he points out that a similar 

 current of action (negative variation) accompanies an excitation, and is 

 often entirely restricted to the latent period preceding the response, as 

 it always is in a stimulated striated muscle. This negative variation 

 is, however, simply a special instance of the general law enunciated by 

 Hermann *, that an excited or injured area in a continuous mass of 

 protoplasm always becomes electrically negative to the uninjured or 

 unexcited portions. Hence the duration of the negative variation at any 

 point corresponds to the length of time the protoplasm remains excited, 

 and if the stimulus is propagated so also will be the negative variation. 



The amount of work done by a contracting muscle represents a very 

 large portion, often as much as one-fourth, of the energy of the food 

 consumed, but the work done by the streaming plasma in plant-cells 

 represents only a very small fraction of the energy of respiration. 

 Moreover, the plasma of a quiescent muscle is at rest, but probably moves 

 on contraction, and rearranges itself within a framework of elastic tubes, 

 whose elasticity forms a prominent factor in the contraction and sub- 

 sequent relaxation. 



Another essential difference is that the liberation of energy and 

 production of heat increases in the contracting muscle, but either remains 

 the same or decreases when rotation ceases. The latter is an instance 

 of inhibition, comparable in a wide sense to the stoppage of the heart's 

 beat produced by the action of certain stimuli upon the inhibitory 

 nervous mechanism. This analogy affords no proof of the existence of 

 any such mechanism in plant-cells, and it is even doubtful whether any 

 special conducting organs normally exist in the form of protoplasmic 



1 Handb. d. Physiol., Bd. I, Th. I, p. 224. 



