130 The Structure of Protoplasm 



apparatus makes it possible to centrifuge a tissue while the com- 

 pression is maintained at any desired level up to 14,000 Ibs./in.- 

 Thus one may measure, by the centrifuge method, the fluidity of the 

 protoplasmic system as a function of pressure. The bomb is divided 

 into two parts; (1) the experimental, or pressure chamber, and (2) 

 the control chamber. A needle valve seals the pressure into the 

 experimental chamber during the period of centrifugation, and since 

 the centrifugal radius is the same for both chambers, the control 

 (atmospheric), and the high pressure specimens are subjected to an 

 equal centrifugal force. 



The second apparatus is the microscope-pressure chamber 

 described by Marsland and Brown in 1936. In this chamber, speci- 

 mens may be viewed during the period of compression at magnifica- 

 tions up to 600 diameters."" Upper and lower windows, 3 mm. 

 thick, permit hght to be transmitted through the chamber to a 

 special objective'^ which, despite an unusually great working distance 

 of 15 mm.,1" possesses a magnification of 15 diameters. Since the 

 specimens in the chamber tend to drop to the upper surface of the 

 lower window, the bomb is used with an mverted microscope, and 

 good images are obtained with oculars up to 20 X- 



III. CELLULAR ACTIVITIES WHICH 

 INVOLVE PROTOPLASMIC STREAMING 



A. AMOEBOID MOVEMENT 



The dependence of this activity upon the structural character- 

 istics of the gel system of the amoeboid cell has been demonstrated 

 by several types of experiment (Brown and Marsland, '36, and 

 Marsland and Brown, '36) . 

 (1) Effects of high pressure, rapidly established 



In this type of experiment, the amoebae were placed in the 

 pressure chamber and then, while under continuous observation, 

 were rapidly compressed at the rate of about 1,500 Ibs./in.- per 



second. 



The first effect of the compression is the cessation of the proto- 

 plasmic flow when the pressure reaches about 4,000 lbs. Then no 

 further change is noted until the pressure reaches approximately 

 6,500 lbs. At this point, within 0.5 second each elongate pseudo- 

 podium undergoes a sudden shrinkage in length and develops a 

 terminal sphere of the type shown in Figure 1. This abrupt and 

 rapid reorganization of the pseudopodium is followed by a more 



