THE SPLEEN IN MARSUPIALS. 



the middle of the convex border of the kidney to the 

 Lateral abdominal wall, and continuous over the kidney 

 with the lieno-mesocolic fold. The attachment of the 

 lieno-mesocolic fold to the left kidney (zygosis) is thus a 

 factor in bringing the spleen into close relation with 

 that organ, and this is more marked in some specimens 

 than in others. In two specimens the pancreas lay 

 ventral to the left kidney, and the renal surface of the 

 spleen was related to the outer part ; but all could be 

 raised off the kidney, as they were suspended on the 

 lieno-mesocolic fold, and this was not attached to the 

 ventrum of the kidney as above described. The fold, 

 however, was really lieno-renal, as its lower attachment 

 was to the dorsal wall at the lower pole of the kidney, i.e., 

 it did not extend to the mesocolon, the lower portion 

 being atrophied. In a smaller variety of Australian 

 Phalanger (Pseudochirus), though the spleen is prac- 

 tically similar to that of Trichosurus, the fixation of 

 structures in the left hypochondrium and lumbar regions 

 is more pronounced. The renal surface of the spleen is 

 in relation with the upper and outer convex surface of 

 the kidney, and the left process of the spleen can be raised 

 slightly oif that organ. The pancreas, however, is seen 

 to be in close relationship with the ventral and outer sur- 

 face of the kidney. In Trichosurus the left distal colon 

 and meso-colon are free of lesser sac, but in Pseudochirus 

 they are included for about 8 cm. This inclusion must be 

 an important factor in approximating colon to spleen, 

 although in Pseudochirus it is associated with a large 

 process of pancreatic tissue in the lesser sac and free 

 from the dorsum. Whilst in Trichosurus the colon and 

 mesocolon are not brought close to the kidney, in Pseudo- 

 chirus the lieno-mesocolic fold is relatively shortened up 

 and the mesocolon is brought in direct relation with the 

 caudal pole of the kidney, so that we find in close connec- 



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