ON THE OLFACTORY SENSE OF BIRDS 



119 



M 



Head tilted 



Swallowed 



Fig. 9. Record of the respiration of goose No. 2. Ethyl mercaptan and water. 



H2O1 



IVl 



Fig. 10. Record of the respiration of goose No. 2. Water and ethyl mercaptan. 



'EZ 



Fig. 11. Record of the respiration of goose No. 2. Skatole. 



UL 



Fig. 12. Record of the respiration of goose No. 2. Skatole. 



Fig. 13. Record of the respiration of goose No. 3. Skatole, 



