318 



STUDY OF PIG EMBRYOS. 



anlages of the ducts, can just be recognized on the lower mesial surface of the 

 Wolffian body near the cephalic end of the organ. In the 20 mm. pig the funnels 

 have lengthened into tubes, which run a short distance caudad, close underneath 

 the Wolffian duct. Figure 215 A is a section through the right Mullerian funnel, 

 F. The mesothelium near the funnel is considerably thickened, forming the so- 

 called tubal band, Ep. The funnel is lodged in a small ridge, Rid, which projects 

 downward from the mesonephros. The Wolffian duct does not appear in the section 

 as it does not extend so far head ward. Figure 215 B is a section farther caudad, 

 to show the oval Mullerian duct, M.D, which immediately underlies the Wolffian 

 duct, W.D, and causes a small protuberance on the surface of the mesonephros. 



V.s.c. Msth 



W.t 



Rid 



W.D 



M.D 



Rid 



FIG. 215. PIG OF 20 MM. TRANSVERSE SERIES 59, A, SECTION 851; B, SECTION 887. 



Ep, Tubal band of thickened mesothelium. F, Funnel-shaped opening of the Mullerian duct. M.D, Mullerian 

 duct. Msth, Mesothelium. Rid, Ridge containing the Mullerian funnel. V.s.c, Sub-cardinal vein. W.D, 

 Wolffian duct. W.I, Wolffian tubules. X 150 diams. 



A short distance farther on the duct ends in a blind point. It is destined to 

 continue its backward elongation until it reaches and joins the neck of the allantois. 

 At just what stage the junction occurs in the pig is undetermined. 



Section through the Posterior Limbs (Fig. 216). Although this section is from 

 a transverse series, yet, owing to the curvature of the body, it shows the spinal 

 cord cut very obliquely. The three layers of the cord, the ependymal, epen, the 

 cinerea or neurone layer, Cin, and the ectoglia are well marked. Something of 

 the dorsal root, D.R, and of the ganglia, G, of a lumbar nerve are also shown in 

 the section. The nerves have already joined together to form a very complex 

 lumbar plexus, sections of portions of which appear at various points. These are 

 all indicated by the reference letter N in the figure, it being thought not desirable 

 to attempt an identification of each component of the plexus. The plexus is more 

 or less symmetrically placed on tho right and left, at about the level of the intes- 

 tine, Reel. The limbs are large projections extending do\w \vard and containing in 



