OLFACTORY REACTIONS IN AMPHIBIANS 649 



such receptors, olfactory in function and responding only to 

 stimuli when the cell surfaces are dry were peculiar only to air 

 breathing animals was the earlier assumption. 



The work of Aronsohn ('86) and Veress ('03) has shown that 

 in man and the higher vertebrates the olfactory epithelium is 

 bathed by glandular secretions and whatever stimulus reaches 

 the receptor must do so in the form of solutions. 



More recently Baglioni ('09), Parker ('10; 11), Sheldon ('11) 

 and Copeland ('12) have demonstrated in aquatic animals the 

 stimuli inducing certain reactions to be identical with those 

 noted in the air-breathing animals. 



If this assumption is valid, as it appears to be, that the olfac- 

 tory receptor is the simplest and least differentiated of receptor 

 neurones and stimulated by extremely dilute solutions, we 

 should find the olfactory organ in Anura readily stimulated. 



That well defined and characteristic motor reactions have 

 not yet been recognized as results due to stimuli varying in 

 quality may be due to lack of observational data and metho'ds 

 of experiment. 



SUMMARY 



1. There is no evidence that toads react to olfactory stimuli 

 pertaining to soil, water, etc. 



2. The character of the food is not differentiated by attendant 

 odors to the degree that the adult toad thus distinguishes it. 



3. Substances of unusual character and odors, when associated 

 with food, do not stimulate the olfactory organs in such a man- 

 ner as to bring the toad to refuse the food. 



4. The presence of such substances in close proximity to the 

 toad, and invisible because of darkness are not repellent in effect 

 on the toad. 



5. Odorstreams specific in character, made to flow over and 

 into the nasal openings stimulate the olfactory sense-organ; such 

 stimulation causing definite motor activities to follow. 



6. Appropriate operations are confirmatory that the stimulation 

 by such odorstream is olfactory. Section of the olfactory tract 

 inhibits the reactions. Olfactory stimulation and reactions are 



