W. J. CROZIER 



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Limulus heart, where even moderate traction applied to a cardiac 

 ganglion was seen to increase the intensity of nervous discharge as 

 reflected in the heart beat. And it is obvious that in experiments 

 concerning permeability {cf. Lillie, 1909) the presence or absence of 

 relatively intense muscular activity, itself employed as an index of 

 excitation, may introduce a complication difficult to evaluate. 



2. Effects of Stimulation. 



Pieces of the mantle of the nudibranch were cut from individuals 

 of medium size. The fragments excised were about 1.5 cm. long. 

 Non-polarizable electrodes, 4 mm. apart, were applied to the pig- 

 mented surface. Current was obtained from a Harvard induc- 

 torium with two Leclanche cells in parallel in the primary circuit, 

 the secondary coil being at "5." The stimulation was purposely 

 made rather severe. The mantle fragments became contracted 

 when stimulated, since they contained smooth muscle fibres. Con- 

 siderable quantities of slimy secretions were expelled from the 

 stimulated surface. After being stimulated the piece of tissue was 

 immersed in an acid solution, and the penetration time was com- 

 pared with that exhibited for a control piece previously unstimulated. 



Experiment 8.33.2. — Four pieces of tissue, each stimulated for 30 seconds, and 

 four control pieces, unstimulated; 0.10 n HNO3; 21°C. 



The pronounced increase of penetrability demonstrated in such 

 tests was found to hold for other acids as well. 



The increase of penetrability is somewhat augmented according 

 to the duration of the stimulation. 



