628 JONATHAN RISSER 



nium and were allowed to remain in the experimental chamber 

 with the toads under the same light conditions as described 

 in the preceding trials. The presence of the odors did not 

 stimulate the toads to seek or avoid the worms in the dark. 

 Again, as observed in the previous trials, the presence of the 

 odorous substance did not deter the toads from taking food in 

 the hght. 



ODOR-STREAM EXPERIMENTS 



1. Apparatus 



From the experiments previously recorded there was no 

 positive evidence that odors were concerned with the taking 

 of food by the toads. Odorous substances when taken into 

 the mouth by accident do not stimulate the receptor organs 

 to the degree of inhibiting the act of deglutition. A possible 

 explanation for this might be sought in the relation of the ex- 

 ternal nostrils to the mouth. Even if the olfactory function 

 were present to but a slight degree, it might be possible to dem- 

 onstrate its presence by leading the odors directly to the nasal 

 opening. If the vapors could be brought directly to the epithe- 

 lial surfaces in appropriate manner, reactions might occur. It 

 seemed desirable to devise some method for doing this. 



After some trials, an apparatus of a satisfactory kind was 

 finally devised. An outline of it is shown in figure 1. The 

 arrangement of the parts is as follows: From the reservoir. A, 

 water displaced the air contained in B. By means of screw 

 clamps at x and y the rate of flow of the water was controlled. 

 The clamp, x, was adjusted for the flow, while clamp y is used for 

 starting and stopping the stream as a whole. C is a small reser- 

 voir in which was suspended a vial, D, containing the odorous 

 substance used. The distal end of the outlet tube, h, was sub- 

 merged in the material contained in D; the air stream carried 

 over and out of C would consequently be impregnated with the 

 odor to be tested. By means of appropriate connections and the 

 nozzle tube, d, three milhmeters in diameter and bent in proper 

 form, the air stream was led into the experiment chamber, E. 

 Elastic suspension of the tube, d, automatically raised the tube 



