ABSTRACT
Terrapins have been trained to olfactory and visual stimuli. The animals are able to discriminate meat alone from meat with amyl acetate, vanillin, eucalyptus or a black figure.
The olfactory discrimination is learned less readily than the visual discrimination under comparable conditions.
Destruction of the olfactory nerves shows that amyl acetate and vanillin are olfactory stimuli. The discrimination to amyl acetate is lost for about 6 weeks after destruction of more than half of the olfactory nerves, and the postoperative feeding behaviour is temporarily altered.
Olfactory lesions do not disturb the discrimination or feeding behaviour of animals trained to a visual situation.
Animals with large olfactory lesions show recovery of the amyl acetate discrimination after 6 and more weeks of postoperative training. It remains to be determined whether the recovery is due to a taste or general chemical discrimination or to surviving olfactory fibres.
The method should prove suitable for studying the olfactory and perhaps other functions of the chelonian forebrain.
The term ‘olfactory stimulus’ has been used in the present context to refer to any stimulus that reaches the central nervous system via the olfactory nerves. Stimuli that reach the nervous system over other paths are classified as taste or general chemical sensation. Hasler (1954) has used the same, classification for his fish experiments.
Habituation is used to refer to a series of positive trials only. During a period of habituation the fright responses that animals show when they are handled wane : there is also a ‘positive’ training which Ihows as an increased readiness to swim from one end of the tank to the other, and to feed.
