The world as seen through the clarifying lens of the 9th Edition of the Encyclopaedia Britannica (1875-1889).

Wednesday, 8 October 2008

33. ii) More fun with pigeons

"Flourens and the older observers were aware of the fact that as successive slices of grey matter are removed from the cerebrum an animal becomes more dull and stupid, until at last all indications of perception and volition disappear. A pigeon in this condition (see fig. 29), if carefully fed, may live for many months ; to quote from Dalton -

"The effect of this mutilation is simply to plunge the animal into a state of profound stupor, in which it is almost entirely inattentive to surrounding objects. The bird remains sitting motionless upon his perch or standing upon the ground, with the eyes closed and the head sunk between the shoulders. The plumage is smooth and glossy, but is uniformly expanded by a kind of erection of the feathers, so that the body appears somewhat puffed out, and larger than natural. Occasionally the bird opens its eyes with a vacant stare, stretches its neck, perhaps shakes its bill once or twice, or smooths down the feathers upon its shoulders, and then relapses to its former apathetic condition."

Similar observations have also been made on reptiles and mammals, but the latter survive the operation for a comparatively short time. In watching such an animal it is difficult to divest one's mind of the belief that it still feels or hears. It may be observed that it rarely makes movements unless stimulated from without. Thus it may remain motionless for many hours ; but if pushed, or gently touched, it moves. As remarked by Prof. M. Foster -

"No image, either pleasant or terrible, whether of food or of an enemy, produces any effect on it, other than that of an object reflecting more or less light. And, though the plaintive character of the cry which it gives forth when pinched suggests to the observer the existence of passion, it is probable that it is a wrong interpretation of a vocal action ; the cry appears plaintive, simply because, in consequence of the completeness of the reflex nervous machinery and the absence of the usual restraints, it is prolonged. The animal is able to execute all of its ordinary bodily movements, but in its performance nothing is ever seen to indicate the retention of an educated intelligence.""

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