The development of the human body; a manual of human embryology . eveloping a cross-connection with its fellow, degen-erates at its anterior end, and, so becoming separatedfrom the ductus Cuvieri, is transformed into the venahemiazygos of adult anatomy (Fig. 150, B and C, vha). The ascending lumbar veins, frequently described as thecommencements of the azygos veins, are in reality secondaryformations developed by the anastomoses of anteriorly andposteriorly directed branches of the lumbar veins. THE VEINS. 287 The Development of the Veins of the Limbs.—The devel-opment of the limb veins of the
The development of the human body; a manual of human embryology . eveloping a cross-connection with its fellow, degen-erates at its anterior end, and, so becoming separatedfrom the ductus Cuvieri, is transformed into the venahemiazygos of adult anatomy (Fig. 150, B and C, vha). The ascending lumbar veins, frequently described as thecommencements of the azygos veins, are in reality secondaryformations developed by the anastomoses of anteriorly andposteriorly directed branches of the lumbar veins. THE VEINS. 287 The Development of the Veins of the Limbs.—The devel-opment of the limb veins of the human embryo requiresfurther investigation, but from a comparison of what isknown with what has been observed in rabbit embryos itmay be presumed that the changes which take place aresomewhat as follows. The blood brought to the limbs bythe arteries is collected into a marginal vein which sur-rounds the free edges of the distal portions of the limb(Fig. 151, A) and passes proximally in two stems, onesituated on the ulnar (fibular) and the other on the radial. Fig. 151.—The Development op the Arm Veins in the , Vena basilica; vc, vena cephalica. It is to be noted that in therabbit the basilic vein at one stage (C) is much reduced in size,but is later re-established.—(Hochstetter.) (tibial) side. In the anterior extremity the radial veinbecomes of less and less importance (Fig. 151, B), and asthe digits develop the marginal vein becomes broken upinto segments and disappears (Fig. 151, C), while theulnar vein persists, forming the basilic vein (vb) of adultanatomy, of which the axillary and subclavian veins arethe proximal continuation. All other veins of the armare secondary or tertiary developments, the cephalic (ve)and other superficial veins first developing and later thedeep veins (vence comites). At first the cephalic vein, 288 THE DEVELOPMENT OF THE HUMAN BODY. passing over the clavicle, empties into the external jugu-lar, but later it forms a connection wit
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
