PHYSICAL ASPECTS OF PROTOPLASMIC STREAMING 



NoBURo Kamiya 

 I. INTRODUCTION 



Protoplasmic streaming is maintained by a motive force which 

 overcomes the viscosity of protoplasm, and in so doing imparts a 

 specific velocity gradient to it. Until now the magnitude of this 

 motive force was not known, nor was it known how it changes. 



The development of a suitable technique has made it possible to 

 measure the absolute value of the motive force generated in proto- 

 plasm. 



The experiments were done on the plasmodia of the Myxomycete, 

 Physaruvi polycephalum. As is well known, the plasmodium of a 

 Myxomycete consists of stationary protoplasm of higher viscosity 

 and less viscous flowing protoplasm, both of which are readily inter- 

 convertible. Streaming is accompanied by changes in the contour of 

 the Plasmodium as a whole. These two processes, streaming of the 

 fluid, inner protoplasm, and change in contour of the whole body are 

 so closely related that one movement necessarily involves the other. 

 One remarkable feature of the protoplasmic streaming in Myxomy- 

 cetes is its comparatively great speed, and especially significant is 

 the characteristic reversal in direction of flow. The velocity of flow 

 changes according to the rhythmic pattern. 



Before proceeding with the subject matter of this paper, it would 

 seem pertinent to state briefly the behavior of protoplasmic flow 

 under locally applied mechanical pressure, which behavior was so 

 characteristic as to lead me to undertake the experiments reported 

 here. 



A cover-glass culture of a plasmodium is inverted on a glass slide 

 with enough water to keep the protoplasm from touching the slide. 

 Then, a certain point on the cover glass is gently pushed down by 

 means of a bent needle affixed to a micromanipulator. When some 

 part of a plasmodium thus mounted first touches, under applied 

 pressure, the surface of the slide, the movement of the interior, fluid 

 protoplasm is strikingly affected. As the mechanical pressure is 

 exerted unequally upon the plasmodium, because of the uneven 

 surface of the plasmodium, and the fact that pressure is applied only 



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