THE ALIMENTARY TRACT 173 
muscular layer and once, in an ostrich, by the penetration 
of a nail. Obstruction of this di\dsion of the stomach by 
impaction of food and stones is not common, but does 
occur. The reason for such obstruction is usually very 
obscure. Sometimes it seems due to the feeding of 
seeds and the like in too finely divided form, whereby food 
and pebbles are taken up together. Some of the smaller 
birds have had in times past too many small pebbles in the 
cages, while others have had too large seeds, thus appar- 
ently trying to use the pebbles to crush them. It would 
seem also that the birds had really eaten too much and 
could not accommodate it in the gullet and gizzard ; this 
seems surely true in three or four Accipitres. Most often, 
however, we have had to fall back upon the inadequate 
explanation of pica or perverted appetite. 
Impacted proventricles and gizzards have been 
observed thirty-four times, in eight of which it seemed 
the sole cause of death, and therefore probably entirely 
due to foreign bodies in food. The theory is accepted 
that dilatation and obstruction will not occur if the motor 
power of the gastric wall be normal and no inflammation 
exist. In this regard we can only discover five birds (the 
mammals will be discussed later) vntln any distinct inflam- 
matory or degenerative disease of this part of the 
anatomy and two with lesions elsewhere which might 
affect the musculature; this leaves the vast majority of 
gastric obstruction in birds unexplained on basis of 
defective motor power, therefore probably dependent 
upon the character of material consumed. The anserine 
birds and parrots are most often affected by this form 
of obstruction. 
Acute or chronic dilatation of the forestomach and 
gizzard is very rare in birds, it having occurred only 
thrice in our records, a finch, a parrot and an owl ; the 
causes were entirely unknown since the cavities were not 
overfilled with food. 
