258 



CHEMICAL SENSES 



10* 



I0 : 



o 



in 



b 10 



>- 



> 



I- 

 o 

 < 



DYE 



GLUTAMIC ACID TRACER 



10 



20 30 



SAMPLE NUMBER 



40 



50 



Figure 13 Movement of tritium-labeled d,-l glutamic acid, com- 

 pared with movement of inert dye through the olfactory sac of a 

 lemon shark. The tracer activity (solid line) is plotted on a semi- 

 log scale and the dye densities (dashed line) on a different scale, 

 to facilitate comparisons of the time course of travel of each sub- 

 stance through the sac. 



