. On the anatomy of vertebrates [electronic resource] . he upper anddextral angle of this au-ricle. The mitral valveis regulated by two shortand thick mammillarycolumnae, ib. k, k, whichsend their tendinouschords to the marginand ventricular surfaceof the valve. The ventricles andauricles present the usual Mammalian proportions and relativethickness of the parietes. Three sigmoid valves are situated atthe origin of the pulmonary artery, and the same number at thatof the aorta. B. Heart of Lissencephala.—In most species of this subclass1the right auricle shows the modifications resulting from t
. On the anatomy of vertebrates [electronic resource] . he upper anddextral angle of this au-ricle. The mitral valveis regulated by two shortand thick mammillarycolumnae, ib. k, k, whichsend their tendinouschords to the marginand ventricular surfaceof the valve. The ventricles andauricles present the usual Mammalian proportions and relativethickness of the parietes. Three sigmoid valves are situated atthe origin of the pulmonary artery, and the same number at thatof the aorta. B. Heart of Lissencephala.—In most species of this subclass1the right auricle shows the modifications resulting from the returnof the blood thereto, as in Lyencephala, by two distinct precavals,of which the left opens alongside the postcaval into the lower(sacral) part of the auricle, as in figs. 401, 402. In the Por-cupine a large i Eustachian fold is on the auricular side of the 1 Capromys is an exception, among the Rodents: at least in the specimen I dis-sected, the blood from the head and fore-limbs entered the auricle by a single precavalvein. cxxx. p. 72. 403. Heart of the Wombat. 520 ANATOMY OE VERTEBRATES. postcaval aperture, and a slight ridge indicates the remains of theupper fold, forming the boundary of the 4 sinus venosus. In thegreat Anteater I observed that the resemblance to the auricularvalve in Reptiles was rather closer:—the entry of the postcavalwas guarded as usual by the Eustachian valve, or homologue ofthe lower of the two semilunar valves between the sinus and theauricle in the Crocodile (vol. i. fig. 339): and here there wasalso a narrower valvular fold or ridge on the opposite side of thepostcaval orifice, answering to the second valve (ib.): a ridge iscontinued from both valves toward the opening of the precaval. Inthe Elephant, also, which shows its rodent affinity in the two pre-cavals, there is, besides the * Eustachian between the orifices ofthe postcaval and left precaval, a remnant of the upper valve ex-tending from the posterior side of the orifice of the
Size: 1362px × 1835px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubject, booksubjectbirds, booksubjectfishes
