Volume 5

Treasury of human inheritance / edited by Karl Pearson, R.A. Fisher, L.S. Penrose.

Date:
1909-
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Treasury of human inheritance / edited by Karl Pearson, R.A. Fisher, L.S. Penrose. Source: Wellcome Collection.

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    quite freely, avoiding all obstacles in its flight; the author observed for example that it flew under chairs without the tips of its wings touching any part of the chair, also when he held a walking stick perfectly still in its path it swerved suddenly when only a few inches from the stick which it did not touch. Hartridge made similar experiments in what he believed to be an absolutely dark room; his bats avoided threads in their path and appeared to know whether the door was or was not sufficiently opened for them to pass through. Whitaker may of course have been mistaken in thinking his bat was at the time blind, but he states that scientists have made similar observations on bats whose eyes had been removed; Hartridge also may have misjudged the absolute darkness of his room, but the fact appears to be fairly well established that the bat avoids obstacles in its flight by some sense or senses other than that of vision in our sense of the word, and whether the particular sense which guides it be that of touch localised in the wing membranes or in the skin of the nose, or whether it be the highly specialised develop ment of the ear, does not concern our argument and the warning it carries. Another fact, which is, in the opinion of the writer, of some significance and cer tainly has a suggestive value, is the absence of all indication of a perception of colour in the daily associations of dogs, cats, horses, cattle and perhaps all mammals, but there appears to be a general consensus of opinion in favour of the belief that birds recognise different colours; indeed, brightly painted screens proved so effective as a lure for the attraction of the red-legged partridges of the Lesghian mountains, that the Russian government some years ago forbade the use of them in order to prevent the extermination of the bird 1 . When we examine the literature it appears that all attempts to demonstrate a perception of colour in mammals (excepting the monkey) have either failed to do so or are extremely unconvincing, whereas for hens and pigeons Hess 2 was able to define the limits of their visible spectrum which coincides, he considers, with ours at the red end and terminates short of ours in the blue-green region towards the short-waved end 3 ; he was able, further, by fastening grain coloured green to the ground and scattering freely other coloured grain, to show that these birds quickly learned that green grains were of no use to them and never attempted to pick them up but quickly removed all the rest; they could evidently distinguish readily between red and green and other colours within the range of their visible spectrum, and the shortening of their range may be partly, if not wholly, accounted for by the absorptive properties of the coloured oil globules in their retinae. Similar observations were made by Hess for certain reptiles 4 . It is quite clear then that the available material concerning the comparative study of retinal structure and of retinal function is at the moment entirely inadequate for the purpose of throwing any light upon the mechanism of colour vision in man, but we hope that this state of affairs will soon be changed when retinal structures are classified on a basis which may be applied to all organisms, and when the need for more cooperation between the zoologist and the physiologist is fully appreciated. Some of the authors not yet referred to whose works have been consulted with regard to this 1 Bibl. No. 238. 2 Bill. Nos. 308, 309, 354, 379. 3 Honigmann confirms this conclusion and further demonstrates a hypersensitivity for the red end of the spectrum. See Bibl. No. 398. 4 Bibl. Nos. 342, 354.