On the unity of structure in the animal kingdom / by Martin Barry.

Date:
[1837?]
Catalogue details

Licence: Public Domain Mark

Credit: On the unity of structure in the animal kingdom / by Martin Barry. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    25/34 (page 19)
    internal or vegetative, and an external or animal portion of the body. The following diagram is intended to illustrate fundamental unity, and the causes of subsequent variety in structure; the latter being acquired in development, and development being represented by curves. Let the point A, re- Fig. i], present the supposed coincidence in funda- mental form, of four germs of the Class Vertebrata. The curves drawn from the point A, to ' /-.• ''-j , / / the points B, C, D, E, Z f'} / represent, respectively, ' ' the development of / V Fishes, Reptiles, Birds, and Mam- /' ,/' mals. The identity of the curves, in curvature, corresponds to iden- tity in the manner of development {i. e. in the manner of his- tological and morphological separation). The lengths of the curves, together with the degrees of un- dulation, measure the degree of' aggregate elaboration attained by each of the above, in the course of its development.* The dotted continuations of the curves, measure the diffe- rences in the degree of elaboration. The different directions of the curves, both general and par- ticular, represent the different directions taken in development; i. e. modifications of the type of the Vertebrata; and serve ro shew, that while there exist resemblances, identities are impos- sible. The amount of divergence, measures the difference in struc- ture, arising from the different directions taken in development, (difference in kind). This illustration is, however, a very coarse one. We cannot, for in- stance, represent the fact, that certain parts of structure in birds, are more wrought out, than con-esponding parts in mammals. The term aggregate ela- boration, has therefore been employed.