STUDY OF SECTIONS OF EMBRYO OF 17 MM. 



307 



R.sy. 



Ao. 



art. 



msth. 



epithelium, the nuclei of which are decidedly larger than those of the mesenchymal 

 cells. The nuclei themselves stain deeply, have well-marked outlines, and very 

 distinct granules in their interior. The protoplasm of the cells also stains some- 

 what with cochineal, carmine, hematoxylin, etc. There is very little mesenchyma 

 Nch. ec.gl. Sp.c. G. N. R.V . 



R.V 



Sym. 



Cce. 



V.msn. 



Gen. 



Glo. 



W.t. 



Som. 



W.D. 



mst. 



In. Li. 



FIG. 209. PIG, 17.0 MM. TRANSVERSE SERIES 51, SECTION 651. 



Ao, Dorsal aorta. art, Glomerular artery. Cce, Ccelom. ec.gl, Ectoglia. G, Ganglion. Gen, Genital 

 gland. Glo, Glomerulus of Wolffian body. In, Intestine. Li, Liver, mam, Mammary anlage 1 . mst, 

 Mesentery, msth, Mesothelium. N, Ventral nerve. Nch, Notochord. R.sy, Ramus sympathicus of 

 nerve. R.V', R.V", Branches of the ventral ramus of the spinal nerve. Som, Somatopleure. Sp.c, 

 Spinal cord. Sym, Sympathetic ganglion. V.msn, Vena mesonephrica. W.D, Wolffian duct. W.t, 

 \Yolffian tubule. X 22 diams. 



in the organ, but each tubule is closely invested by vascular endothelium; hence the 

 tubules are separated from one another only by blood spaces, which, morphologi- 

 cally speaking, are portions of the cavity of the cardinal vein. These blood spaces 

 are highly characteristic and are typical sinusoids. The intertubular circulation 

 of the Wolffian body is, so far as known, always sinusoidal. The,, aorta, Ao, is 

 seen in the figure to give off a small branch, ' art, which runs toward the Wolffian 

 body. There are numerous such branches, each one of which may be traced to a 



