OBSERVATIONS MADE IN CANINE MEDICINE. 
309 
almost invariably reveals a remarkably healthy appearance of 
the tympanum and canal contiguous thereto. 
In no other case can it be more difficult to tell beyond a 
question where eczema ends and catarrh begins than in these 
cases; nor is there perhaps another condition which more 
clearly shows the prudence of the older pathologists who 
claimed eczema to be a catarrh of the skin. 
If we review the labors of those who have toiled upon these 
cases in the interest of bacteriology we find exceedingly little, 
indeed I may say nothing, which warrants us in setting these 
cases outside the pale of skin diseases. 
Like eczema of other locations, we are forced to look upon 
it as being mainly induced by external irritation, rather than as 
arising from internal conditions, anatomical or physiological in 
nature. It is very generally said by authors to be an outcome of 
“filth.” Well, I am perfectly willing to grant that the so- 
called filth is a factor in its development, but if such were more 
than a mere factor, and its real cause, I am satisfied that every 
animal would necessarily suffer, inasmuch as all alike would be 
sufficiently exposed. 
This we know is not the case here, any more than that filth 
begets in all cases eczema in other parts. There are other in¬ 
fluences quite as important as filth itself (which is at best a very 
ambiguous term in medicine) in the production of this eczema 
of the ears, and they are such as more directly determine the 
conditions under which such filth exists. 
L^pon these conditions depends the whole matter of impuri¬ 
ties. It is only necessary for me at this time to recall the num¬ 
ber of obstinate cases of this trouble coming under my observa¬ 
tion, which have developed in animals subject to the most 
scrupulous care to prevent this accumulation of the so-called ear 
filth, by frequent washing, etc., to readily understand how great 
the difficulty an extremely small amount of impurity can cause 
when conditions favor, and how great and varied the same can 
be, and still be powerless to do harm where conditions are un¬ 
favorable to it. 
