900 
FOREST AND STREAM. 
[Dec. 8, 1906. 
The Dog’s Boilers and their Fuel. 
BY WOODS HUTCHINSON, A.M., M.D., IN OPEN COURT. 
The secret of life lies in the gift of drink¬ 
ing in sunshine, either raw as plants do, or 
worked up into what we call foods, as animals 
must, and using its warmth for selfish purposes. 
The green stuff of plants catches the sunlight, 
which sets to work building the stem-leaf house, 
and then storing it with starch and sugar. Then 
comes the animal and, most greedily, eats up the 
plant, crystallized sunshine and all, and uses it 
first to build his own body-house, then to move 
it about and warm it. 
The first and most important need of the dog- 
engine is plenty of fuel. It was to move about in 
search of this, that his racing machine grew up. 
So that his body is like a locomotive, not only 
in having a running gear and “wheels,” but a 
“fire box’’ as well, in which his food fuel can 
be burnt and turned into heat and horse-power, 
or more correctly, “dog-power.” As you would 
expect in any fire box, there are two openings, 
one for taking in fuel, the other for getting rid 
of stuff that will not burn properly, called ashes 
or waste. 
'These are the opposite ends of the body, so 
that the dog’s fire box is in the form of a longish 
tube, known in Latin as the alimentary canal, or 
in plain English, food tube. This is the form of 
the body-furnace in all backboned animals, and 
most backboneless, though some of the simplest 
and earliest of these have a mere pouch, with 
but one opening. 
But the food tube of the dog is very far from 
being a simple canal, of uniform caliber from 
mouth to anus. As you look at it, you see that 
about a foot down from the mouth it balloons 
out into a pear-shaped pouch, the stomach, then 
becomes small again and thrown into a large 
number of coils, the last of which is somewhat 
larger than_ the. others. Altogether in fact, in¬ 
stead of being just the length of the body, it is 
between five and six times as long. Is there 
anything in the food of the dog to explain this 
state of affairs? Why does he need a stomach- 
pouch, and coils of intestine? 
A pouch is used to store or carry things in, 
and if you recall the kind of food that the dog 
lives upon, you see at once how much he needs 
a place where he can stow away a quantity at 
one time to be digested at leisure. When he 
catches a deer, or a woodchuck, all that he is 
sure of is what he can eat on the spot. He is 
compelled to be greedy, for if he leaves any of 
it till the next day, or even next meal, it is almost 
sure to be stolen before he comes back. So he 
gorges himself with all that his stomach will 
hold. Indeed if you can come upon a wolf while 
he is feasting on the body of a heifer, or year¬ 
ling colt which he has pulled down, you can 
sometimes ride or run him down, inside of a 
mile, so enormously has he loaded down his 
stomach, not merely for present but also for 
future use. 
This then is the primary use of a stomach,' a 
storage or delay place for food, until it can be 
gradually absorbed. But would not this delay 
be an excellent time for beginning to melt it 
for absorption? In an early and simple stomach, 
like the fish’s, where the food is chiefly other 
fishes, shrimps, worms, water weeds and such 
like soft watery things, which need only to be 
kept warm and moist, to melt of themselves, you 
will find little else in its lining but a pavement 
of thickish, smooth cells. But if you will look 
at the lining of the dog’s stomach, you will see 
that it looks thick and velvety, and with a mag¬ 
nifying glass you can make out swarms of tiny, 
little openings, like pinpricks, dotted all over 
it. These are the mouths of tiny pouches of 
the inner cell sheet, known as glands, which 
manufacture and pour out a sour juice, called 
the stomach, or in Latin, gastric juice. 
This has a curious power of melting meat, and 
can dissolve a moderate stomachful in two or 
three hours, though the huge gorges that the 
wild dog takes may require two or three days, 
during which he sleeps most of the time, in his 
burrow, or on a sunny hillside, and doesn’t like 
to be disturbed. Indeed it is a rule, with wolf- 
hunters, that unless you can get your hounds to 
the place of his last kill within twelve or fifteen 
hours after he has left the carcass, so. that the 
pack has a chance of “cold trailing” him to his 
lair, it is better to wait two or three days, until 
hunger drives him abroad again, for as long as he 
lies still, he, of course, makes no trails, and to 
beat the woods on the mere chance of stumb¬ 
ling upon him, would be like hunting a needle 
in a haystack, unless you happen to know just 
what thicket he “lies up” in. 
This explains the meaning of that simple, pear- 
shaped pouch in his food tube, which we call the 
stomach. But what of the long coils, not unlike 
a live garden hose, into which the rest of the tube 
is thrown? Evidently these are not adapted for 
storing the food or for letting it rest in one place 
until it can be melted; but if you will open the 
tube and look at a portion of its lining under 
the microscope, you will get a suggestion as to 
the meaning of this loop of coil form. Instead 
of being, like a stomach, dotted all over honey¬ 
comb fashion with tiny little openings of glands, 
the lining of this part of the tube, known from 
its narrowness as the small intestine, ■ is covered 
with tiny, fingerlike projections standing up all 
over its surface; and it will not take you long 
to guess that like fingers elsewhere the purpose 
of these is to pick up things, and that the busi¬ 
ness of this part of the intestine is to take up 
or absorb the food which has been melted in the 
stomach. But why should it be so long? A 
simple experiment will answer the question. 
If you will take a sheet of blotting paper, hold 
it on a gentle slant and endeavor to pour a stream 
of ink down it, you will find that although it 
runs briskly enough for the first inch or two, 
before it reaches the bottom of the sheet the 
current stops completely, as it has all been soaked 
up by the paper. Now this is, roughly speaking, 
almost exactly the process which is going on in 
the dog’s small intestine, and for the matter of 
that in the intestine of all animals including our¬ 
selves, and it follows, that the longer the tube 
of living blotting paper, the more completely will 
the melted food be absorbed. But it must not be 
supposed, that nothing else but absorption of the 
melted food takes place in the small intestine. 
A good deal of further melting goes on as well, 
for although the lining membrane in the greater 
part of the intestine has lost most of the gland 
pouches which pour digestive juice into the 
stomach, yet this is only because, so to speak, 
these have all been piled together in two great 
masses, each of which opens by a tube nearly 
the size of a quill into the bowel, just beyond the 
stomach. The largest and solidest of these, on 
the right side of the tube, is known as the liver; 
the smaller and more loosely built, upon the left 
and behind the stomach, is the pancreas. 
These are simply very complicated gland 
pouches which have budded out from the lining 
of the tube, like a little plant or shrub whose 
stems are hollow. The leaves of the shrub are 
the cells which manufacture the digestive juice, 
the stalks are the smaller collecting pipes, and 
the stem is the discharge tube or duct of the 
gland through which this digestive fluid is poured 
into the food tube. 
But it will strike you at once that the huge 
solid liver is much larger than would be needed, 
simply to manufacture and pour into the canal 
the bitter brownish or greenish bile; and your 
suspicion would b.e quite correct, for in addition 
to aiding digestion in this way, the liver also re¬ 
ceives the blood from the walls of the food tube 
loaded with nourishment which has been soaked 
up out of it, and sends this on another step in 
the direction of being turned into blood and body 
fuel. It also filters out and neutralizes many 
poisons which get into the blood both from the 
food tube and from the waste processes of the 
body cells. 
Then if you will look at a food tube which 
has been blown up and allowed to dry, you will 
see that after the coils of the garden hose part 
of it comes a third, very much wider portion, 
curiously puckered and pleated along its sides, 
known as the large intestine. In the lining of 
this you will find no fingers whatever and very 
few gland openings, and this, together with the 
curious way in which its walls are pouched and 
puckered by three narrow bands of muscle fibre, 
which run along its outer wall like draw strings 
in the mouth of a bag, would suggest that'it 
is merely a place of detention for the remains 
of the food until its moisture and such traces of 
nourishment as the fingers of the small intestine 
have left in it have been soaked out of it. 
The saving of this loss of moisture is really a 
very important thing, for none of our body cells 
can live unless kept continually in water, and salt¬ 
water at that. We are still sea animals in ninety- 
nine per cent, of our structure. When the parts 
of the food, which are too hard or tough or 
coarse to be melted by the digestive juices, have 
had all the nourishment and surplus moisture 
sucked out of them, they are discharged through 
the second or terminal opening at the end of 
the food tube known as the anus. Like other 
furnaces, the body fuel tube is constructed with 
two openings, one to receive fuel and the other 
to get rid of ashes or waste. 
If then the food tube of the dog has grown 
into its present shape to match the amount of 
food which is put into it. we would expect that 
animals living upon widely different food would 
be found to have developed a somewhat different 
shape both of stomach and intestine, and if you 
will look at this drawing of a sheep’s stomach, 
you will see at once that this is just what has 
occurred. 
In place of a single pear-shaped swelling or 
pouch in the course of the food tube, you find 
a most complicated looking bag of four pouches 
or chambers opening into one another, the whole 
being nearly four times the size of the stomach 
of a dog of the same weight. But to remember 
the difference in the food is sufficient to explain 
this at once. 
The dog, of course, under natural conditions, 
lives almost entirely upon meat which is quite a 
concentrated food, and three or four pounds 
would make a fairly satisfying meal. A sheep, 
on the other hand, lives upon grass, leaves and 
hay with a little grain in the winter time, and 
these foods are extremely coarse and low in 
nourishment value. It would take from twenty 
to forty pounds of green grass to make a satis¬ 
factory meal for a sheep as against the three or 
four pounds of meat which a dog of the same 
size requires, so that just as a place to store food 
the sheep’s stomach needs to be much larger. 
Not only this but coarse hay and such foods are 
much harder to melt in the stomach, more difficult 
of digestion; indeed, neither the dog nor our¬ 
selves could digest enough of them to live more 
than a few days upon a diet of grass, leaves or 
green vegetables, and this you see is matched by 
the numerous divisions of the sheep’s stomach. 
So hard of digestion is a grass diet, that it is 
not sufficient to bite it off, chew it and swallow 
it, but it has been found necessary to put it 
through the curious process of returning from 
the stomach to the mouth, to be carefully chewed 
