64 PLAN OF MAMMALIAN: LIVER CHAP. 
as this. In Phalanger maculatus the two sections of the gut are 
as nearly as possible equal in length, while in Phascolarctos the 
large intestine is considerably longer than the small, the lengths 
bemg respectively 160 inches and 111 inches. It is common 
among the Marsupials and also among the Rodents for these 
proportions to exist, 7.e. for the large intestine to be as long as, 
or longer than, the small. But there 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 mammals. 
Appended to the alimentary tract are three glands or sets of 
glands. Opening into the mouth cavity are the salivary glands, 
which are of enormous 
size in Anteaters, and 
small or absent in 
Whales. In their num- 
ber and position these 
elands 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 
Fic. 42.—Diagrammiatic plan of the liver of a Mammal t 3 me 
(posterior surface). c, Caudate lobe; cf, cystic the diver is, however, 
fissure ; dv, ductus venosus; g, gall-bladder; dc, & ally characteristic 
; zi Ae ea 3" enera characteristic 
left central lobe ; 7/, left lateral lobe; 7/f, left © gor ai E 
lateral fissure ; p, portal vein entering transverse of mammals. It is 
fissure 3 re, right central lobe 3 rl, right lateral lobe ; divided as a rule into 
rif, right lateral fissure ; s, Spigelian lobe ; w, um- ‘ Z 
bilical vein: ve, post-caval vein. (After Flower a night and a left half, 
am ae ase 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 lobes. In addition 
to these, two other divisions are often to be seen—the Spigelian 
and the caudate lobe. The liver is less divided in Cetacea and 
