THE MAST-CELL GRANULE 



of cover slip is lowered on to the field which is to be observed, the microscope 

 re-focused and the switch closed. 



For a moment nothing happens. Then, one after another the mast cells 

 'tense 1 , round up and, literally, explode— a most dramatic and astonishing 

 sight. However, it was quickly evident that this is not an 'electrophoretic' 

 separation: the 'explosions' begin at the cathode, spread to the centre of the 



Fig. 43 



Simple apparatus for testing the effect of an electrical 



field on mast cells in rat mesentery. The preparation 



is bathed in physiological salt solution. 



field and stop (Fig. 44). By replacing the tissue with a piece of filter paper 

 soaked in a dilute solution of an indicator fluid ('Universal Indicator', B.D.H.) 

 it is evident that the origin and extent of the disruption of the mast cells 

 correspond exactly to the wave of sodium hydroxide which is released 

 electrolytically from the salt solution in which the preparation is bathed; this 

 also begins at the cathode and stops at the centre of the field. The mast cells near 

 the positive pole, the acidic (HC1) half of the field, remain intact. If the current 

 is reversed they, too, undergo disruption. The whole phenomenon can be 

 reproduced by running a drop of N/10 sodium hydroxide under the cover slip 

 of a fresh preparation (Fig. 45). 



117 



