24 DR. E, LONNBERG ON DIGESTIVE [Jan. 14, 



It is thus evident that the contents of the ileum must pass 

 into the colon, and from there, when the sphincter mentioned 

 above relaxes, into the caecum. It is also evident that no large 

 pieces can pass through the narrovs^ opening into the caecum. A 

 comparison between the contents of the colon proves this state- 

 ment completely. A sample of the contents of the colon taken 

 2 cm. from the ileo-csecal valve consists chiefly of large pieces of 

 the chitinous integument of insects, setse of such animals, etc. 

 A sample from the caecum consists only of the tiniest particles 

 which cannot be measured or identified. The narrow opening 

 between the ca3cum and the colon serves accordingly as a filter. 

 The large indigestible remains are kept back in the colon, the 

 fluid and the fine pai-ticles svispended in the same pass into the 

 caecum, where, no doubt, an absorption of the fluid takes place, 

 after which the indigestible remains are forced back to the colon 

 to be expelled with the faeces. The function of the caecum may 

 thus be termed absorbing and desiccating. The large intestine 

 acts nearly in its whole extent as a rectum, as the faecal matter 

 is already formed into balls at a distance of only 2 cm. from the 

 ileum (text-fig. 6). 



Text-fig. 6. 



Caicum of Petaurns hreviceps. 



c, ciecum ; i, ileum; co, colon. Valvula ileo-colica is seen to protrude into the 

 colon, and a bristle is inserted through the narrow opening of the cseco-colic 

 sphincter. 



In Fhalanger, on the other hand, it can be assumed with 

 certainty that the caecum has a digestive fvmction, which may be 

 concluded from the fact that it is provided with large glands. 

 The great length of the colon makes it probable that it has 

 digestive as well as reabsorbing powers. 



The dimensions of the different tracts of the intestine in a 

 marsupial young of Petanrus hrevicejis, measuring 63 mm. in total 

 leng-th without tail, were as follows: — Small intestine 185 mm., 

 caecum 17 mm., and large intestine 43 mm. If these measure- 

 ments be compared with those of the young animal itself (without 

 tail) the relation is expressed by the following percentages : — 290, 

 26, and 68. Fi'om this it may be seen that all three parts are 



