The cockatiel would have been a rare bird at the time, "and one whose life would never in reality have been risked in an experiment such as this". It did not become well known until after it was shown in illustrations to the accounts of the voyages of Captain Cook in the 1770s. Prior to Cook's voyage, cockatiels had been imported only in small numbers as exotic cage-birds. Wright had painted one in 1762 at the home of William Chase, featuring it both in his portrait of Chase and his wife ("Mr & Mrs William Chase") and a separate study, "The Parrot". In selecting such a rarity for this scientific sacrifice, Wright not only chose a more dramatic subject than the "lungs-glass", but was perhaps making a statement about the values of society in the Age of Enlightenment. The grey plumage of the cockatiel also shows much more effectively in the darkened room than the small dull-coloured bird in Wright's early oil sketch. A resemblance has been pointed out between the group of the bird and the two nearest figures and a type of depiction of the Trinity found in Early Netherlandish painting, where the Holy Spirit is represented by a dove, to which God the Father (the philosopher) points, while Christ (the father) gestures in blessing to the viewer.