. The comparative anatomy of the domesticated animals. Veterinary anatomy. 918 Fig. DIAGRAM OF THE CIR- CULATION AT THE COMMENCEMENT OP THE FORMATION OF THE PLACENTA : SEEN FROM THE FRONT. a, Venous sinus re- ceiving all the sys- temic veins; 6, Right auricle ; 6', Left auricle ; c, Right ventricle; c', Left â ventricle; (?, Bulbus aorticus, subdividing into, e, e', e", Bran- chial branches; f,f, Arterial trunks formed by their con- fluence ; g, g', Vena azygos superior; /', h', Confluence of the superior and inferior azygos; j, Vena cava inferior; k, k', Vena azygos inferior; m, De
. The comparative anatomy of the domesticated animals. Veterinary anatomy. 918 Fig. DIAGRAM OF THE CIR- CULATION AT THE COMMENCEMENT OP THE FORMATION OF THE PLACENTA : SEEN FROM THE FRONT. a, Venous sinus re- ceiving all the sys- temic veins; 6, Right auricle ; 6', Left auricle ; c, Right ventricle; c', Left â ventricle; (?, Bulbus aorticus, subdividing into, e, e', e", Bran- chial branches; f,f, Arterial trunks formed by their con- fluence ; g, g', Vena azygos superior; /', h', Confluence of the superior and inferior azygos; j, Vena cava inferior; k, k', Vena azygos inferior; m, Descending aorta; n, n, Umbilical arte- ries proceeding from it; 0, o', Umbilical veins; q. Omphalo- mesenteric vein; r, vesicle, t; v, Ductus EMJBBYOLOGY. by the ductus arteriosus. To sum up, the foetus never receives pure arterial blood into its organs, this being always mingled with venous blood, the mixture taking place at several points : 1, By the foramen of Botal; 2, In the aorta by the ductus arteriosus; 3, In the liver by the ductus venosus. The head and neck are the parts which receive the purest arterial blood, a fact which explains the predominance of the anterior over the posterior portion of the body of the foetus. At birth, the conditions of existence being suddenly changed, marked modifications take place in the cir- culatory apparatus. The lungs become the organs of respiration, and rapidly increase in capacity; the pul- monary artery dilates to give passage to the blood that flows to them; while the ductus arteriosus is obliterated, in order to isolate the arterial from the venous blood. This separation of the two fluids also takes place in the liver by the atrophy of the ductus venosus, and in the heart by the occlusion of the foramen of Botal; though, according to M. Goubaux, that orifice frequently remains open in young animals. Its persistence has also been noted in the human adult. Notwithstanding the pre- sence of this foramen, the circulation cannot be m
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