THE SPLEEN IX MARSUPIALS. 



lomys) (page 148), though conforming more to the primi- 

 tive Mammalian type, yet resembles the human so closely 

 as to be at times almost indistinguishable, and so the so- 

 called anterior, posterior, and superior angles of the 

 human spleen become significant. These all have their 

 prototypes in the Platypus. Two spleens are illustrated, 

 taken at random from full-time fetuses (page 154). As 

 one might expect, the anterior process (/ e. ventral, right 

 process of the Platypus) is well defined, while the pos- 

 terior (i.e. dorsal, left process of the Platypus) is poorly 

 defined. In both, fissures are seen defining the body from 

 the processes. From the point of view of biology, i.e. 

 function, the human spleen of the text-books cannot be 

 accused of affording much information. Post-mortem 

 examinations made for a period of six years with Dr. S. 

 Strachan at a benevolent home for the aged showed me 

 the great relative frequency of perigastric adhesions, 

 perisplenitis, and old left pleuritis, all of which would 

 profoundly modify shape. To throw light on the signi- 

 ficance of shape it would be better if young subjects were 

 chosen. One naturally wonders whether different por- 

 tions of the Mammalian spleen have different functions. 

 There is no biological evidence of this, nor can it be said 

 to Vse borne out by histological examination, although 

 important differences were noted in the spleen in the dif- 

 ferent members of the orders described. As regards the 

 fixation of the human spleen, this, it must be borne in 

 mind, is associated with fixation of the distal colon and 

 left pancreas. The attempts made by nature can be 

 studied in the Monotremes and Marsupials. In a study 

 of the peritoneum of the members of these two orders, 

 three primary folds are noted, which are traced in vary- 

 ing degree throughout the Mammalia, and play an im- 

 portant part in the fixation of the gut, which is coadjusted 

 to the erect posture: — 



151 



