Sketches of Natural History of Ceylon eBook

J. Emerson Tennent
This eBook from the Gutenberg Project consists of approximately 590 pages of information about Sketches of Natural History of Ceylon.

Sketches of Natural History of Ceylon eBook

J. Emerson Tennent
This eBook from the Gutenberg Project consists of approximately 590 pages of information about Sketches of Natural History of Ceylon.

In the gardens and grounds toads[1] crouch in the shade, and pursue the flies and minute coleoptera.  In Ceylon, as in Europe, these creatures suffer from the bad renown of injecting a poison into the wound inflicted by their bite.[2] The main calumny is confuted by the fact that no toad has yet been discovered furnished with any teeth whatsoever; but the obnoxious repute still attaches to the milky exudation sometimes perceptible from glands situated on either side behind the head; nevertheless experiments have shown, that though acrid, the secretions of the toad are incapable of exciting more than a slight erythema on the most delicate skins.  The smell is, however, fetid and offensive, and hence toads are less exposed to the attacks of carnivorous animals and of birds than frogs, in which such glands do not exist.

[Footnote 1:  Bufo melanostictus, Schneid.]

[Footnote 2:  In Ceylon this error is as old as the third century, B.C., when, as the Mahawanso tells us, the wife of “King Asoka attempted to destroy the great bo-tree (at Magadha) with, the poisoned fang of a toad.”—­Ch. xx. p. 122.]

In the class of Reptiles, those only are included in the order of Batrachians which undergo a metamorphosis before attaining maturity; and as they offer the only example amongst Vertebrate animals of this marvellous transformation, they are justly considered as the lowest in the scale, with the exception of fishes, which remain during life in that stage of development which is only the commencement of existence to a frog.

In undergoing this change, it is chiefly the organs of respiration that manifest alteration.  In its earliest form the young batrachian, living in the water, breathes as a fish does by gills, either free and projecting as in the water-newt, or partially covered by integument as in the tadpole.  But the gills disappear as the lungs gradually become developed:  the duration of the process being on an average one hundred days from the time the eggs were first deposited.  After this important change, the true batrachian is incapable any longer of living continuously in water, and either betakes itself altogether to the land, or seeks the surface from time to time to replenish its exhausted lungs.[1]

[Footnote 1:  A few Batrachians, such as the Siren of Carolina, the Proteus of Illyria, the Axolotl of Mexico, and the Menobranchus of the North American Lakes, retain their gills during life; but although provided with lungs in mature age, they are not capable of living out of the water.  Such batrachians form an intermediate link between reptiles and fishes.]

The change in the digestive functions during metamorphosis is scarcely less extraordinary; frogs, for example, which feed on animal substances at maturity, subsist entirely upon vegetable when in the condition of larvae, and the subsidiary organs undergo remarkable development, the intestinal canal in the earlier stage being five times its length in the later one.

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Sketches of Natural History of Ceylon from Project Gutenberg. Public domain.