208 The Structure of Protoplasm 



though restricted, continues to take place within the protoplasmic 

 expanses at both ends of the connecting strand, which are spread 

 into more complicated forms than those schematically shown in 

 Figure 5, a and b. 



Morphologically, the two parts of protoplasm in the different 

 compartments are still connected, but functionally, they behave just 

 as if they were two independent plasmodia, as long as movement in 

 the connecting strand is suspended. 



As in the case of an artificial change in velocity, the cessation of 

 protoplasmic flow for a period of time by uninterrupted adjustment 

 of the balance-pressure also causes no visible abnormalities in the 

 protoplasm. Nor is there any indication of physiological disturbance 

 even after more than two hours, during which time the flow is 

 stopped. When the balance-pressure is released by opening the 

 stop-cock (SC in Fig. 5) , the protoplasm in the connecting strand 

 immediately starts to flow. The velocity depends upon the inherent 

 motive force in the protoplasm at the moment of release. 



V. RELATED PROBLEMS 



The experiment reported above gives a means of attacking prob- 

 lems covering important subjects of protoplasmic research. 

 The Capillary Method as a New Means of Measurement of Proto- 

 plasmic Viscosity. 



It is impossible to make slime mold protoplasm flow through a 

 glass capillary without fatal resuhs, but through its own capillary, 

 such as a connecting strand, the protoplasm can flow quite normally. 

 A dumbbell-shaped plasmodium consisting of its own capillary and 

 two "reservoirs" of protoplasm is, as it were, in itself a capillary 

 viscometer. If one releases a balance-pressure of known value and 

 compares the velocities of protoplasmic flow at the time of release 

 in a treated and a control plasmodium, one can estimate the relative 

 viscosity of the interior flowing protoplasm under controlled con- 

 ditions. As the inner diameter of the connecting strand is not kept 

 exactly the same, some correction for this is needed. 



The diameter and length of the connecting strand are both 

 determinable; the motive force responsible for the flow can now be 

 measured. By determining the velocity of protoplasmic flow through 

 the capillary of known diameter and length under known shearing 

 stress (motive force) , it seems not impossible to evaluate even the 

 absolute viscosity of protoplasm by applying Poiseuille's Law. 

 In passing, another point may be mentioned, namely, the 



