THE ALIMENTARY TRACT 199 
Thus food is of no moment as a disturber of the alimen- 
tary tract, while bacteria and parasites are high in 
importance. The gastric segment is more often attacked 
than any other portion and slightly more often than in the 
nearest order, Carnivora. These unusual figures deserve 
explanation, to which purpose it will be necessary to con- 
sider the anatomy of the organ and to discuss why 
bacteria and parasites stand so high in etiology. 
Marsupials are divided into six families in our classi- 
fication (see page 44) which in regard to their diet, 
range from largely carnivorous (the first two) through 
those choosing mixed insects, fruits and vegetables (the 
second two) to those eating vegetables and grain (the last 
two). The stomach of these animals does not vary exactly 
according to their diet, the first four, opossums, dasyures, 
bandicoots and wombats, possessing an organ closely 
similar in outline and construction and resembling the 
carnivorous variety, while the phalangers and kangaroos 
have a stomach entirely different from the first four 
although somewhat similar to one another. The first 
group has a round or irregularly elliptical organ with the 
esophagus and pylorus close together along the lesser 
curvature. The wombats have a bank of glands sur- 
rounded by a capsule, near the cardia. The stomach of 
the first four animals is divided into cardiac, fundal and 
pyloric parts by the construction of their mucosa, the 
first mentioned division being a high, rounded pouch, 
rumen-like, well to the left. The phalanger 's stomach is 
more elongated, the two openings well separated and a 
fissure is found in the right end of the lesser curvature 
which serves to separate the pyloric part from the rest. 
The Macropodidae all have a stomach resembling the 
human colon in being elongated, with longitudinal bands 
gathering it into sacculations. There is a distinct eso- 
phageal section to the left with a blind sac suggesting an 
ungulate rumen, a long tubular fundal, and a sacculate 
pyloric division. 
