646 JONATHAN EISSER 



In no case in the course of the feeding experiments was cog- 

 nizance taken of the unusual substances coming into the mouth 

 to the degree that food was ejected or regurgitated. The ex- 

 perience cited by Knauer ('75) of toads refusing decomposing 

 earthworms is probably referable to tactile stimulaticJn. The 

 nature of the organisms serving as food for the toads under 

 natural conditions is such, that materials differing in texture 

 markedly from the normal might be sufficient to cause refusal. 



To establish any connection between food used by toads 

 and the possible odors inherent to the food seems difficult 

 at present. Although evidence is negative, this is qualified 

 by the fact that the data are really not sufficient to establish 

 any conclusion on this question. Natural foods are apparently 

 taken indiscriminately. Stimulation of the receptors may take 

 place; the presence of such stimulation and the effect are not yet 

 demonstrable. 



Our inability to recognize the quality of particular motor 

 reactions following certain stimulations does not argue against 

 the absence or refinement of reactions. 



The experiments of Graber ('85) were such as to allow no 

 great value to be attached to them. The unmodified methods 

 used for forms differing so greatly in phylogenetic position and in 

 habit with the very doubtful reactions as recorded, speak against 

 the acceptance of his data as important. 



To a similar degree the experiments of Aronsohn ('86) on 

 odors and respiration are of little value in indicating the use of 

 the olfactory organ in anurans. His experiment does not pre- 

 clude stimulation of the trigeminal nerve. His choice of sub- 

 stances and the manner of experimentation favor the possibility 

 that the fifth nerve is involved. The instance mentioned by 

 Conradi ('01) has not had confirmation of any kind. In the 

 experiments described, the presence of abnormal odorbearing 

 substances has not given origin to stimulation sufficiently strong 

 to inhibit the desire for food. 



In all experiments carried out with the lower animals and 

 their reactions toward solutions or vapors there exists the pos- 

 sibility that solutions or vapors are more dilute than was in- 



