THE ALIMENTARY TRACT 175 
There were no obvious reasons for assuming any damage 
to the gastric motor mechanism. 
Gastric Ulcees. 
Gastric ulcer, so-called peptic or round ulcer of the 
stomach, having a chronic course and leading to radiating 
scars of the mucosa is not common in the lower animals, 
but frequent enough in the human being. The form of 
ulcer in question has at present no adequate explanation, 
or at least there is no one cause which will answer for all 
cases. Local injuries from ^\ithin or without the stomach, 
bacterial embolism, entrance of bile through the open 
pylorus and many other factors have been named in the 
causation but can seldom be used in any given case. In the 
lower animals with their relatively frequent parasitic 
infestation, another factor is added. In analysis of our 
statistics I have separated ulcerative gastritis from para- 
sitic and mycotic ulcerations and from peptic ulcers ; the 
first is discussed in later paragraphs. Parasitic ulcers of 
the stomach occur chiefly in our native marsupial, the 
opossum, and in some Carnivora ; physaloptera, strongy- 
lus, ascaris, and gastrophilus have been found. The 
kangaroos are frequently affected (8 cases) with an 
acute or subacute ulceration of the gastric wall, without 
much general gastritis. The lesion is peculiar in appear- 
ance. The youngest ulcers are black or dark gray, flat 
necroses of the mucosa alone and indeed the process very 
frequently penetrates no deeper. Older lesions spread 
laterally and may be preceded by a very narrow 'con- 
gested line but there is no raised edge nor does there seem 
to be submucous infiltration. If the process be rapid 
a loose dirty slough may form. Certain of the advanced 
cases of Kangaroo mycosis will present more infiltrative 
lesions of the gastric wall leading to large and well 
defined necrotic areas ; they may at times penetrate the 
whole wall outward. (See page 580.) 
