248 MICROSCOPIC AX.ITOMY OF THE ORGAX& 



by the construction of wax models after the method of Born. 

 In general, there are two parts in the tubule, a secreting and a 

 collecting segment. This was recognized first by Joh. Miiller. 

 In the pig the collecting tubule possesses two convoluted parts, 

 while the secreting portion is a large loop in the central part 

 of the organ. The epithelium is characteristic in these two 

 parts, "being low and cubical in the collecting segment, and 

 columnar in the secreting portion. 



The blood supply of the Wolffian body is derived directly 

 from the aorta. This has been worked out in pigs' embryos 

 (MacCallum). The arteries enter at the medial border of the 

 gland and break up to form the glomeruli. From these many 

 efferent arteries proceed in a radial manner toward the periph- 

 ery. Around the tubules they form a fine capillary network, 

 which empties into three series of veins. Two of these run 

 on the periphery of the organ toward the medial border, over 

 the dorsal and ventral surfaces, respectively. The other series 

 of veins leaves the Wolffian body by the same path as that 

 taken by the arteries in entering. A distinct blood vascular 

 unit can be observed. 



At a certain stage in the development of the embryo, which 

 differs in different species, the Wolffian body begins to undergo 

 retrogression. The tubules degenerate, and the glomeruli 

 become occluded. The anterior tubules alone in the male 

 remain connected with the Wolffian duct, and grow in size and 

 complexity to form the head of the epididymis. The tail of 

 the epididymis and the vas deferens are derived from the Wolff- 

 ian duct. The posterior tubules of the Wolffian body form the 

 paradidymis or organ of Giralde. 



In the female the Wolffian duct degenerates. The anterior 

 part persists usually with the parovarium. When the whole 

 duct persists, it is known as Gartner's canal. The Wolffian 

 body in the female persists in its anterior (sexual) part as the 

 parovarium (epoophoron, organ of Rosen miiller). The tubules 

 making this up increase considerably in size. The posterior 

 tubules (renal part) disappear with the exception of a few 

 tubules, known as the paroophoron. 



