On the relation between the quantity of brain and the size of the body in vertebrates / by Eugène Dubois ; [communicated by H. Zwaardemaker].

  • Eugène Dubois
Date:
1914
Catalogue details

Licence: In copyright

Credit: On the relation between the quantity of brain and the size of the body in vertebrates / by Eugène Dubois ; [communicated by H. Zwaardemaker]. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    liglit jirevailing in the water that makes other senses than the optical one predominate in tliese Mammals, as likewise in the Fishes, and probably in the Crocodiles (hearing very ipiick), in comparison with Amphibia and most Reptiles. In the Fishes also the olfactory organ and especially the sense-lines are predominant. This has caused angmentation of the quantity of brain, because the surfaces of the mentioned predominating organs of sense (in opposition to the eye, which forms definite images) increase simply projiortional to the super- ficial dimension of the animal (consequently with the exponent of correlation 0.66. . .). So in these animals a veiy considerable increase of the quantity of brain does not signify a high degree ' of organisation. Calculated by means of the ex[)onent of correlation 0.66...) h becomes for Whalebone-Whales 0.07, for Toothed Whales 0.20 and for Seiils 0.18. In the Snakes and the Slow Worm and likewise in the Eels, on the contrary, the great length of the body is the cause of the low value of k, though this does not therefore indicate an inferior degree of organisation. In proportion to the weight of the body the not specialised segmental sensn-motorical unities are loo equivalent for a representation in the bi-ain, pro[)orlional to that of other Reptiles and Fishes. The l)ody becomes thereby, as if were, to a certain amount, a ballast for the brain. This is in a more literal sense the case in the Tortoises. In the shell-bearing Vertebrates and also in the elongated animals the intlnence of the factor in the analysis has thus diminished. In the Eels a second cause of diminntion of the quaniity ot brain exists moreover, in iheii'life as animals of darkness, l)y the disa[)pearance for the greater part of the eye-factor S^'~^ in the analysis 1j and at the same time of tlie eye-factor in the analysis .1 (as in the Hats). On account of the latter civcnmstance their r becomes — 0.66. The influence of the not segmentally constituted eye in itself remains iri all cases resti'icted, from the nature of the factor which depends on it, and is thus less capable of increase. Even the Hoi'se, which possesses an absolutely larger (day-) eye than the Elephant, rises still little above the average level of k for Mammals. On the other hand can the other factor the segmental factor in analysis Jk, grow, as it were, endlessly with the development of “specific sense-energies” in the ditferent segments. The tactile organs have therefoi’e always the lead with the highei' organisation of the nervous system. 25 November 1913.
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