. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 60G ANATOMY OF VERTEBEATES. numbers and increase of size: and as the fitness of the vascular surface for respiration decreases, the developement of the gills progresses. The branchial arches appear, three in quick succes- sion, from behind forward, and branchial tubercles bud from them in like order. The mouth and the branchial slits being now opened, the arches move rythmically, so as to produce branchial currents: the blood is yellowish, and the discs begin to show the flat oval shape. As the vitellicle decreases, its
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 60G ANATOMY OF VERTEBEATES. numbers and increase of size: and as the fitness of the vascular surface for respiration decreases, the developement of the gills progresses. The branchial arches appear, three in quick succes- sion, from behind forward, and branchial tubercles bud from them in like order. The mouth and the branchial slits being now opened, the arches move rythmically, so as to produce branchial currents: the blood is yellowish, and the discs begin to show the flat oval shape. As the vitellicle decreases, its circulation is changed, or merged into the portal hepatic system; and now that through the branchial buds begins. The change of the vitelline for the branchial circulation relates, in a general way, to that from the confined to the free state of the young fish: but no such alterations of the circulating or breathing systems attend the escape of the fisli from the egg as mark extrication in the Reptile and Bird, or birth in the Mammal. Vitelline respiration, carried on in ovo by means of the imbibed water between the outer and vitelline tunics, continues to operate for a longer or shorter jieriod after the little fish is free, according to the species, and also according to the indi'^'idual constitution in the same species. Each branchial bud is at first a solid cell-mass, and is excavated to receive the blood with blood-discs in single file : secondary tubercles bud forth at right angles to the primary ones, through which similar blood currents flow : the primary buds become the stems of the leaflets into which the secondary ones are developed, and the cartilaginous axis of the arch and stems next appears. The pseudo-branchia also shows itself behind the eye, in the form of flattened elongated folds, through which the blood courses at first in a few vascular loops. In the Anabas, and probably other Labyrinthibranchs, the epibranchial reservoir, fig. 325, retains a com- parative
Size: 2046px × 1221px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1860
