THE OLFACTORY REACTIONS OF THE NEWT 265 



in the reactions just described? To answer this question it 

 became necessary, first, to ascertain in what way the stimulus 

 reaches the receptors, and, secondly, after preventing any possi- 

 bility of olfactory stimulation, to compare reactions then with 

 those already recorded. 



Certain intermittent mouth movements of Diemyctylus are 

 conspicuous. These consist of a rather slow expansion of the 

 floor of the mouth, followed by a sudden contraction, at which 

 time the mouth is slightly opened. If carmine suspended in 

 water is squirted from a pipette over the snout, it is drawn in 

 through the external nares as this expansion progresses, and 

 expelled from them, and from the mouth, when the contraction 

 follows. Normally, therefore, any solution capable of produc- 

 ing olfactory stimulation flows through the nasal chambers, 

 passes through the internal nares, and enters the mouth, and 

 later a portion of it is expelled in a reverse direction by the 

 same paths. 



To prevent the flow of water through the olfactory chambers, 

 the snout was first thoroughly dried, and then the external 

 nares were covered with a thin layer of a celloidin preparation 

 know commercially as "Cur-a-cut." The day after experiment- 

 ing with the bags, the five animals tested were treated in this 

 w r ay. On the following morning one of them had lost the cap 

 of celloidin, through shedding its skin, and another took no 

 interest in meat which was offered it. The remaining three 

 followed and snapped at meat, and exhibited normal behavior 

 in every way. These three were tested for an hour with the 

 two bags as before, the positions of the two being exchanged 

 every fifteen minutes. The reactions to the bag containing meat 

 were as follows. Animal A nosed it 3 times but did not bite it. 

 B nosed it twice and left it both times. C nosed it 8 times and 

 deserted it in every instance except the first, when it was snapped 

 at about 10 times. The cheese cloth bag was nosed once by A, 

 and twice by C. Five hours later the experiment was repeated, 

 after all three had followed filter paper attached to the end of 

 a probe. A nosed the cheese cloth bag once, B nosed it once 

 and the baited bag 3 times, and C nosed each 4 times. Once C, 

 after nosing the baited bag, snapped at it 8 or 9 times, but in 

 all other cases there was no seizing reaction. Thus, in the 20 

 responses to the bag containing meat, the seizing reactions oc- 



