432 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



drains the right side, and, like its fellow, enters the ductus Cuvieri at 

 the sinus venosus. 



THE DUCTLESS GLANDS. 

 THE SPLEEN. 



This organ lies in Amiurus, between the posterior end of the 

 stomach and the anterior end of the genital organs. It is in contact' 

 with the peritoneum covering the ventral surface of the air-bladder, 

 and is itself surrounded by peritoneum. The long axis of the gland 

 which is parallel to the same axis of the body, measures when the 

 organ is distended 20 mm., the short diameter 13 mm. It is slightly 

 divided into two lobes, a posterior large lobe and an anterior small 

 lobe. The surface next the air-bladder is concave, the ventral sur- 

 face convex. The right margin, which lies near the median line of 

 the body, is thick and rounded, but the gland thins out toward the 

 left margin where the points of the lobes nearly touch the left body 

 wall. The hilum is on the concave dorsal surface where the artery 

 and veins enter together, and run side by side throughout the gland 

 until the finer branches are reached. This arrangement agrees with, 

 that of the higher Vertebrates, but it is not universal in fishes, e. g., 

 Anguilla 1 , in which the arteries lie across the veins. The vessels 

 spread themselves out, fan-like, from three or four trunk-stems, but 

 these in the case of the veins do not unite into a single splenic vein 

 but enter separately the portal vein, which runs in immediate contact 

 with the surface of the gland. Indeed, one commonly finds three or 

 four patches of small openings close together in the wall of the portal 

 vein, the larger branches of each centre having entered without join- 

 ing. A small vein usually arises from the ventral surface of the 

 anterior lobe, and may enter the portal vein direct or join one of the 

 mesenteric veins just before its junction with the portal. 



The surface of the spleen presents a perfectly smooth appearance 

 in some individuals, while in others raised papillae are visible to the 

 naked eye. In the former granular-looking nodules can be seen 

 thickly imbedded in a clear, reddish matrix, while in the latter they 

 are much less distinct. The reason for this difference will be better 

 understood after a description of the internal structure. 



1 C. Phisalex — Structure et texture de la rate, chez I' Anguilla communis. Comptes Rendus 

 1884, Vol. XCVII., p. 190. 



