POWER OF ADHESION — OCTOPUS SUCKERS 



393 



theoretical maximum suction calculated for the eight suckers is 

 shown by the dots in curve B. The observed breaking forces 

 for these eight suckers are designated by the crosses that afford 

 the basis for curve A. At all points curve A lies below curve B 

 and this relation is what should be expected, for it is quite 

 impossible that a sucker acting purely as such should at sea 

 level exert more than one atmosphere of pressure. 



300 



250 



gm 150 



Fig. 1 Plottings of the observed breaking forces (A) and of the theoretical 

 maximum suction (B) of suckers of different sizes (table 1); the ordinates repre- 

 sent grams, the abscissae square millimeters. 



If in any sucker the breaking force were equal to the theo- 

 retical maximum, that sucker could be said to have an efficiency 

 of 100 per cent. Such, however, is never the case, for, as is 

 shown at the bottom of table 1, the efficiency of these suckers 

 is never higher than 70 per cent of the maximum and may fall as 

 low as 45 per cent, with an average on the eight readings of 

 56 per cent. This efficiency appears to be rather higher for the 



