John Bruce MacCallum 357 



The vei7is of the Wolffian hody arising from the capillary networks 

 aronnd the tubules are represented in Fig. 12. They gather together 

 in two directions. A large number join to form veins which proceed 

 towards the periphery of the organ, while the rest enter large veins 

 which leave the Wolffian body by the hilus where the arteries entered. 

 The surface veins are large branching vessels which run somewhat paral- 

 lel with the tubules and divide the whole organ roughly into lobes. 

 Their course on the ventral aspect of the organ is shown in Fig. 13. 

 Arising from between the tubules they course over the surface and pass 

 under the Wolffian duct. Figs. 12 and 13. On the ventro-medial sur- 

 face of the organ they join together to form three or four large trunks, 

 which enter a common vein at the medial border. From the dorsal re- 

 gion veins present a somewhat similar picture. They usually gather 

 together into four large vessels, two of which drain the middle third of 

 the gland, while the other two drain the anterior and posterior thirds. 

 Eunning along the dorso-medial surface. these venous trunks join with 

 the veins from the ventro-medial surface and enter the inferior vena 

 cava. In addition to these surface veins, there is a series of central 

 veins which leave the Wolffian body at the medial border. One of 

 these veins is shown in Fig. 12. It is made up of the junction of 

 several small branches derived from the capillary plexuses around the 

 tubules. Passing down on the dorsal side of the glomeruli, it joins with 

 the superficial veins to enter the common trunks. 



Fig. 14 shows the relations of these three series of veins and their 

 relation to the veins of the testis and kidney. 



It is necessary to note particularly the disposition of the efferent 

 arteries as shown in Fig. 12. As mentioned before, they pass out 

 from the glomeruli in a radial direction. Each artery in this way occu- 

 pies a territory of its own, and from all sides its small branches form 

 capillary networks which collect to form the veins. This is a repetition 

 of what has been noted in many organs, namely, the formation of blood 

 vascular units with an artery in the centre of each and veins at the 

 periphery. In a transverse section, such is as represented in Fig. 12, 

 six or seven units can be observed. The arterial end of each capillary 

 plexus can be easily distinguished from the venous end by a difference 

 in structure just as the arteries and veins can without difficulty be recog- 

 nized in a single injection of the Wolffian body. The venous end of 

 this network is shown in Fig. 15. This figure is intended to represent 

 a thick section of three tubules, the walls of which are seen obliquely. 

 A fine plexus of irregular venous capillaries covers the walls and gives 

 evidence of the remarkably rich blood supply of the organ. 



