354 ANIMAL.. PHYSIOLOGY. 
There is, however, a recognized non-nitrogenous crystalline 
body known as excretin, which contains sulphur, salts, and 
pigments, and that may rank perhaps as a true excretion of 
the intestine. : 
It is well known that bacteria abound in the alimentary 
tract, though their number is dependent on a variety of circum- 
stances, including the kind of food and the condition in which 
it is eaten. These minute organisms feed, of course, and to get 
their food produce chemical decompositions. Skatol and indol 
are possibly thus produced, and give the fecal odor to the con- 
tents of the intestine. But as yet our ignorance of these mat- 
ters is greater than our knowledge—a remark which applies to 
_ the excretory functions of the alimentary tract generally. 
Pathological.—The facts revealed by clinical and pathological 
study leave no doubt in the mind that the intestine at all events 
may, when other glands, like the kidney, are at fault, undertake 
an unusual share of excretory work, probably even to the length 
of discharging urea. 
Obscure as the subject is, and long as it may be before we 
know exactly what and how matter is thus excreted, we think 
that it will greatly advance us toward a true conception of the 
vital processes of the mammalian body if we regard the ali- 
mentary tract as a collection of organs with both a secreting 
and excreting function; that what we have been terming ab- 
sorption is in the main, at least, essentially secretion or an allied 
process; and that the parts of this long train of organs are 
mutually dependent and work in concert, so that, when one is 
lacking in vigor or resting to a greater or less degree, the others 
make up for its diminished activity ; and that the whole must 
work in harmony with the various excretory organs, as an 
excretor itself, and in unison with the general state of the econ- 
omy. Weare convinced that even as an excretory mechanism 
one part may act (vicariously) for another. 
Of course, in disease the condition of the feeces is an indica- 
tion of the state of the digestive organs; thus color, consistence, 
the presence of food in lumps, the odor, and many other points 
tell a plain story of work left undone, ill-done, or disordered 
by influences operating from within or from without the tract. 
The intelligent physician acts the part of a qualified inspector, 
surveying the output of a great factory, and drawing conclu- 
sions in regard to the kind of work which the operatives have 
performed. 
