OLFACTORY REACTIONS IN AMPHIBIANS 635 



toads than to fishes. This estabhshed an effective hindrance to 

 the respiratory current, therefore it was found impracticable. 

 If the stitches were not placed deeply, the muscular movements 

 of the nostril soon caused the thread to cut through the margins. 

 Furthermore, complete closure of the nostrils was apparently 

 fatal in several preliminary trials. 



Filling the nasal aperture with melted vaseline was only 

 partly successful, entrance to the capsule being prevented by the 

 nostril valves. The vaseline could be "troweled" into the opening. 

 It was evident from the actions of the animals that the vaseline 

 was discomforting. The toads showed decided restlessness and 

 attempted to wipe their heads. 



Some tests were made with toads so treated. When both 

 nostrils had been successfully closed, no reactions traceable to 

 odorous substances could be observed. If only one of the 

 nostrils was closed, the odorstream, when directed upon the open 

 nostril, was effective in causing a reaction. 



Clove oil and pennyroyal were the substances used in the 

 tests with the nostrils partly or wholly closed, these having been 

 most efficient in calling forth reactions in the normal toads. 



To be certain of the assumption that the reactions noticed 

 with the odorstream were called forth by the stimulation of the 

 olfactory receptor, operations of two kinds were performed on the 

 toads. 



In one of the operations, the olfactory tract was severed. 

 In the other, it was necessary to section the ophthalmic branch 

 of the fifth nerve. After etherization, the olfactory tracts were 

 severed at the anterior border of the eyeball. The ophthalmic 

 branch of the trigeminal was cut by piercing the integument 

 of the optic capsule at the anterior inner angle of the orbit and 

 cutting across the floor of the orbit. After recovery, only the 

 specimens reacting normally to other stimuli were used for the 

 tests. 



Toads in which the olfactory tracts had been severed did not 

 react to the odorstream. If partly buried in the sand, they were 

 undisturbed by odors coming through the tube. The head was 

 not drawn down, nor did they move away from the tube. One 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. Ifi, NO. 4 



