. Text-book of zoology for schools and colleges. Zoology. 212 TERTEBEATE ANIMALS. The heart in fishes may be regarded as essentially a hrancliial or respiratory heart, being concerned chiefly â with driving the venous and impure blood to the gills. It con- sists in almost all cases of two cavities, an auricle and a ventricle (Fig. 104). The auricle («) receives the venous blood vrhich has passed through all the various parts of the body, and propels it into the ven- tricle (v). From the ventricle pro- ceeds a single great vessel (the "branchial artery"), the base of which is usually
. Text-book of zoology for schools and colleges. Zoology. 212 TERTEBEATE ANIMALS. The heart in fishes may be regarded as essentially a hrancliial or respiratory heart, being concerned chiefly â with driving the venous and impure blood to the gills. It con- sists in almost all cases of two cavities, an auricle and a ventricle (Fig. 104). The auricle («) receives the venous blood vrhich has passed through all the various parts of the body, and propels it into the ven- tricle (v). From the ventricle pro- ceeds a single great vessel (the "branchial artery"), the base of which is usually developed into a muscular cavity, the " bulbus arte- riosus" (jTi), which acts as a kind of additional ventricle. By the ventri- cle and bulbus arteriosus the venous blood is driven to the gUls, where it is subjected to the action of the wa- ter. The aerated blood is not re- turned to the heart, but is driven from the gills through all parts of the body, the propulsive force neces- sary for this being derived partly from the heart, and partly from the contractions of the muscles between which the blood-vessels pass. The Fie. 104.âDiagram of the Circuk- essential peculiarity of the circulation te:'fs\IlreBentol"Te' of fishes consists in this, that the ar- â penous system is left light, a An- terialized blood returned from the ncle, receivTiig the Tenous blood ... , iji from the body; i> Ventricle; m gllls IS propelled through the gCn- Syrc^^?g?h^.:n?rbtd eral vessels of the body (systemic tothe gills (»); c Great systemic vessels) without beinff Sent back to vessel, carrying the pm-e blood .i n'. xji x ix i to the tissues. the heart, in the JLiancelet, alone of all fishes, there is no single heart, and the circulation is eflFected by means of contractile dila- tations situated upon several of the vessels. In the Mud- fish (JLepidosiren) the heart consists of two auricles and a ventricle. In all cases the blood is cold, or, in other words, has a t
Size: 970px × 2578px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
