ELECTROPHYSIOLOGICAL INVESTIGATION 93 



was preliminary, using the amputated antenna and stimulation with syn- 

 thetic Bombykol on a glass rod as in the initial experiments (Schneider and 

 Hecker, 1956 ; Schneider, 1957). We are now repeating this work with 

 refined methods. The living animal is mounted so that recording is pos- 

 sible with circulatory and respiratory systems intact. Under these cir- 

 cumstances it is possible to record EAG's for many hours or days (Block, 

 Boeckh and Schneider, unpublished). We also changed the stimulating 

 method by using fluted filter paper impregnated with known amounts of 

 lure substance. The fiher paper pieces are put in short glass tubes mounted 

 in front of the air outlet (Fig. 3a). Such cartridges can easily be exchanged 

 during the course of an experiment. 



3 



mV 



2 - 



lO-'f^ W-9 10-'^ W-5 W-^ 10-'> 10^ W^ gland 



Fig. 6. The relationship between Bonihyx male EAG amplitudes and concentra- 

 tions of the four geometrical isomers of hexadekadienol (from Block, Boeckh 

 and Schneider, unpublished). 



The results demonstrate that the earlier curve (cf. Fig. 7 in Schneider, 

 1962, with Fig. 6) is only one of several response types obtained with the 

 Bombyx antenna. To compare the earlier curve with the new ones done 

 with the refined stimulation method, the following consideration is neces- 

 sary. Only about 1/100 of the amount of substance scaled on the abscissa 

 in Fig. 7 of Schneider (1962) actually sticks to the tip surface of the glass 

 rods. Therefore 10"Vg ml solvent actually means about 10"^'' -^g of 

 substance per glass rod tip. This 100-fold dilTerence permits comparisons 

 between concentrations on glass rods and filter paper. 



The new stimulus-response function (Fig. 6) is more complex than 

 expected. Only in the higher concentration range does the response rise 

 with the logarithm of the stimulus concentration, while in the lower range 

 this relationship is rarely found. The response to the isomers varies but 



