. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. the branchial arches, and ultimately form a broad disc, the body of the os hyoides, the anterior margin of which on each side is di- lated into a scutiform process, and the posterior margin bears two bony appendages, which are, in fact, the posterior cornua of that bone. Such are the changes which this bone un- dergoes during the gradual passage of the amphibious animal from the tadpole state, in which it represents the class of fishes, to its perfect or reptile condition; and it affords a most interesting instance of th
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. the branchial arches, and ultimately form a broad disc, the body of the os hyoides, the anterior margin of which on each side is di- lated into a scutiform process, and the posterior margin bears two bony appendages, which are, in fact, the posterior cornua of that bone. Such are the changes which this bone un- dergoes during the gradual passage of the amphibious animal from the tadpole state, in which it represents the class of fishes, to its perfect or reptile condition; and it affords a most interesting instance of the manner in which the true nature of an organ, existing under ambiguous circumstances in one class of animals, is often clearly illustrated by its cha- racters, or, as in the present instance, by its transformations, in another. The minute filiform branchiae, which are appended to the tadpole of the frog im- mediately behind the head, have essentially the same structure as is observed in the gills of the perennibranchiate family, as the siren and the proteus, though in a different form. In the proteus each branchia consists of three principal divisions or branches, from each of which proceed seven or eight leaves, again sub- divided into numerous regular leaflets form- ing the ultimate divisions of the branchiae, on which the extreme capillary branches of the vessels ramify, and in which the blood under- goes its necessary change. A minute rami- fication of the branchial artery, conveying the impure blood from the heart, enters each leaf- let at its base, (Jig. 27, a.) and passes, along Fig. its shorter or inner margin, giving off capillary branches in its course, which, after meandering over the surface of the leaflet, and commu- nicating with each other in various directions, pass over to the opposite margin of the leaflet, and reunite in a corresponding ramification of the branchial vein (6), which passes out at the base to combine with the corresponding branches from
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