64 



PLAN OF MAMMALIAN LIVER 



as this. Ill Fhalanycr raacidatus the two sections of the gut arc^ 

 as nearly as possible ec[ual in length, while in Fhascolarctos the 

 large intestine is consiileralily longer than the small, the lengths 

 heing respectively 160 inclies and 111 inclies. It is common 

 among the Marsupials and also among the liodents lor these, 

 proportions to exist, i.e. IVir the large intestine to be as long as, 

 or longer than, the small. But tliere are so many exceptions 

 that no general statements can be extracted from the facts. 



Some few details will be found in the systematic part of this 

 book. Mr. Chalmers Mitchell has brought forward some reasons 

 for associating a great length of large intestine with an archaic 

 systematic position, in the birds at any rate. The facts here 

 briefly touched upon are not at variance with the extension of 

 such a view to the manii rials. 



Appended to the alimentary tract are three glands or sets of 

 glands. Opening into tlie mouth cavity are the salivary glands, 



which are of enormous 

 size in Anteaters, and 

 small or a,bsent in 

 Whales. In their num- 

 ber and position these 

 glands are character- 

 istic of mammals. Into 

 the intestine open the 

 ducts of the pancreas 

 and liver, two glands 

 which the mammals 

 share with lower verte- 

 brates. The form of 



Fk;. 42. — DiagraiiHiuitic plan of the liver of a Mammal . 



(posterior surface). c. Caudate lol)e ; rf, cystic the liVer IS, howeVCr, 



fissure; rfr, ductus venosus ; //, gall - bladder ; ic, generally characteristic 



left central lobe ; //, left lateral lobe ; l/f, left 

 lateral fissure ; 2'j portal vein entering transverse 

 fissure ; re, right central lobe ; H, right lateral lobe ; 

 rlf, right lateral fissure ; s. Spigelian lobe ; >/. um- 

 bilical vein ; w, post-caval vein. (After Flower 

 and Lydekker. ) 



of mammals. It is 

 divided as a rule into 

 a right and a left half, 

 the line of division 

 being marked by the insertion of the umbilical ligament, a 

 vestige of the primitive ventral mesentery. Each half is again 

 commonly subdivided into central and lateral lol)es. In addition 

 to these, two otlier divisions are often to be seen — the Spigelian 

 and tlie caudate lolje. The liver is less divided in Cetacea and 



