WOLFFIAN BODIES 



309 



It is generally believed that the Wolffian bodies of mammalian embryos are active 

 renal organs, producing a form of urine which collects in the allantoic sac. In pig 

 embryos this sac and the Wolffian bodies are both unusually large. MacCallum (Amer. 

 Journ. Anat., 1902, vol. i, pp. 245^59) notes that the tubules of the Wolffian body in 

 the pig "show a very distinct division into a secretory and a conducting part." In 

 the human embryo, however, the allantois is very small and the Wolffian bodies de- 

 generate early, before the kidney can become functional. Therefore Felix (Keibel and 

 Mall's Human Embryology, vol. 2) regards the question as settled. The Wolffian 

 body " does not function as an excretory organ"; but he adds, "This does not, of course, 

 imply that it may not have been active in another manner unknown to us." 



Veins of the Wolffian Body. In determining the arrangement of the 

 large veins of the abdomen, the Wolffian bodies are of fundamental 

 importance. They are supplied by the posterior cardinal veins which 

 pass from the tail of the embryo, on either side of the aorta, to the heart. 



I/, c. c. 



h. a 2. 



W.B 



i I.' 



il 



FIG. 305- THE TRANSFORMATION OF THE POSTERIOR CARDINAL SYSTEM OF VEINS. 



a. c., Anterior cardinal; as. L, ascending lumbar; az., azygos; c., caudal; c. s., coronary sinus; h., hepatic; 

 h. a. z., hemiazygos; h. az. a., accessory hemiazygos; il., common iliac; in., innominate; j., jugular; 

 K., kidney; I.e. c., left common cardinal; m. s., median sacral; p. c., posterior cardinal; r. c. c., right 

 common cardinal; s. c., subcardinal; scl., subclavian; sp., spermatic; sr., suprarenal; sup., supra cardinal; 

 T., testis; v. c. i., vena cava inferior; v. c. s., vena cava superior; W. B., Wolffian body. 



Before entering the right atrium of the heart, they are joined by the 

 anterior cardinal veins from the head, thus forming the right and left 

 common cardinal veins, or "ducts of Cuvier." As each posterior cardinal 

 vein extends along the dorsal side of the Wolffian body, it sends branches 

 in among the tubules, and these unite ventrally on either side in the 

 subcardinal vein (Fig. 305, A). Thus each Wolffian body is lodged in a 

 venous loop formed by the posterior cardinal and subcardinal veins, and 



