THE SPLEEN IN MARSUPIALS. 



(2) Left, lower, or colic surface. — This is separated, 

 from the gastric surface by the gastro-splenic omentum, 

 and from the renal and gastric by the lieno-mesocolic fold 

 with pancreas, and more posteriorly the renal ridge, since 

 the renal concavity extends to the left extremity. A well- 

 defined fissure is seen a little below its middle, which, 

 extending inwards, serves to define the left process. This 

 surface corresponds to the right ventral and left dorsal 

 processes of the Platypus, the notch on the edge leading 

 to the fissure representing the original interval between 

 the two. It is related to the distal colon, and when dis- 

 tended the stomach is seen to be related to the upper or 

 ventral half (i.e. above the fissure), which portion is in- 

 cluded in the gastric surface of the human. 



(3) Dorsal or renal surface is the narrowest of all 

 the surfaces and corresponds to the body and left posterior 

 process. It is really a concavity for the upper part of the 

 left kidney, and can be regarded as an accommodation 

 effect. The concavity may extend almost along the whole 

 length or be only limited to the lower four-fifths, since in 

 cases with a well-developed left hepatic lobe the upper 

 end of the spleen may be curved over towards the inner 

 surface. The result of renal accommodation or pressure 

 is to define on the inner and dorsal aspect of the spleen a 

 ridge or margin — renal ridge — best defined below, where 

 it forms a distinct projection or angle. This ridge 

 separates the renal and gastric surfaces and, with the 

 lieno-mesocolic fold, the renal from the colic below. 



Interpretation of the Foregoing Facts. 



A study of the spleen in these two orders throws light 

 on the significance of shape of the human spleen and on 

 the correlations associated with its fixation in the left 

 hypochondrium. The spleen of the Wombat (Phasco- 



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