OLFACTORY REACTIONS IN AMPHIBIANS 643. 



by the olfactory organ, attempts were made to inhibit such 

 stimulation in various ways. This was found to be rather 

 difficult and in the light of the earlier attempts the evidence 

 was not very convincing. The diminutive size of the tadpoles 

 is the principal factor militating against successful operations. 



Cutting the olfactory tract is the method by which inhibition 

 may be made absolutely certain. In this method the chief 

 difficulty lies in determining the proper degree- of anesthetization 

 for the operation and subsequent revival of the animal. Chlore- 

 tone of 0.1 per cent was used for this purpose, as the tadpoles 

 could be brought into a vessel with fresh water and revived. 

 After being anesthetized the tadpoles were bedded in a bit of 

 absorbent cotton held in the hand, and with a needle the cranial 

 case was pierced in the median line anterior to eyes. The shock 

 attendant upon the operation or the manipulation was dis- 

 astrous in most cases, and only a few specimens survived. Within 

 a few days these tadpoles became less vigorous, and finally all 

 succumbed. 



The few individuals so operated upon and tested for reactions re- 

 sulting from stimulation to the olfactory sense organ did not give 

 sufficient evidence from which satisfactory conclusions could be 

 drawn. 



In another manner the inhibition of the stimulation and the 

 reactions was also attempted. The external nares of the toad 

 tadpole are comparatively large and it was possible to fill the 

 nares with white vaseline, the tadpoles being bedded in moist 

 absorbent cotton. Tadpoles so treated showed the presence of 

 the vaseline to be disturbing in effect. The plugs prevent the 

 respiratory stream from entering the nasal openings, the swim- 

 ming movements are not so vigorous as under normal conditions, 

 the chief endeavor of the tadpole being to free itself from the 

 disturbing material. The temperature of the water is to be taken 

 into account here, as the vaseline could be removed quite readily 

 by placing the tadpoles in water slightly warmed. As soon as 

 the vaseline has been dissolved the tadpoles again act in normal 

 manner. This method of treatment was made use of in the first 



