MOOEE’S EUEAL NEW-YOEKEE: AN AGEICULTUEAL AND FAMILY JOUENAL. 
^rof. loliMtoivs IwtnrM, 
On the General Belations of Science to 
PRACTICAL AGRICULTURE. 
LECTURE SEVENTH. 
The Relation of Chemical Physiology to the An¬ 
imal—Its Food and its Growth. 
Gentlemen ; —The subject which I pro¬ 
pose to introduce tliis evening is an exceed¬ 
ingly wide one, as indeed I may say of all 
the subjects of which I have treated. At 
the same time, I think the points I shall be 
able to present this evening are so plain and 
intelligible that you can see plainly the 
width of the subjects of which I treat. You 
will recollect that at our last meeting I pre¬ 
sented to you the composition of the ele¬ 
mentary part of the plant; and I showed 
you, that if you take any part of a plant and 
burn it, that by far the largest portion burns 
away; that the part that burns away con¬ 
sists of four elementary substances, carbon, 
hydrogen, oxygen, and nitrogen—these 
three last being difierent kinds of air. I 
showed you, also, how they differed and how 
they were to be distinguished. It is neces¬ 
sary to re-introduce this, to make you ac¬ 
quainted with what is called the ultimate 
composition of the organic parts of plants, 
animals and soils. I wish to make use of 
these words, and unless previously explain¬ 
ed you would not be able to follow them. —• 
First, I draw your attention, not to the ele¬ 
mentary constituents of plants, but to the 
substances that exist in the plants which 
we eat; for example, the great mass of this 
rod consists of woody fibne; then, if you take 
a grain of ground wheat you know that it 
contains much starch; that is anothci' sub¬ 
stance that the plant produces. The sugar 
cane produces sugar; this sugar exists in 
aU plants. These substances all consist of the 
elementary bodies spoken of. There is no 
nitrogen in these I mention, but others don- 
tain it. Now, of the crops we cultivate these 
three substances, woody fibre, starch and 
sugar constitute a very large proportion.— 
But before I show you of what they con¬ 
sist, and in what proportions, I must explain 
to you the nature of the important substances 
existing in the plants which we cultivate for 
food. 
If you take a quantity of wheat flour and 
make it into a dough, and put this dough 
on a piece of muslin tied over a glass, and 
pour water on it, the water will pass through 
the muslin in a milky form. If you con¬ 
tinue the process until the water passes thro’ 
qmte clear, a substance will remain, which 
the chemists call gluten. The milky sub¬ 
stance which passes through the muslin, 
falls to the bottom in the shape of a white 
powder—that is starch—thus I seperate 
wheat flour into starch and gluten. Now, 
this gluten contains all four of the elemen¬ 
tary bodies I have named—it contains about 
16 per cent of nitrogen—hence the nitrogen 
in the atmosphere is of great importance in 
the growth of wheat. Take any vegetable 
substance—the straw of wheat or of this 
piece of Avood; and it contains a great quan- 
ty of fibrous substance called woody fibre— 
that exists in all plants. If you take this 
gluten and put it into spirits of wine and 
heat it, you can extract from it a quantity 
of oil. So with Indian corn, or oats, and 
from the stalk and straw of either you can 
extract more or less oil. We have then, 
first of all, the woody fibre, we have starch, 
and gluten, and oil; these four are import¬ 
ant to the nourishment of animals and exist 
in all plants. But before showing the im¬ 
portance of these substances to the growing 
animal, I must show you the proportions in 
wliich they exist. 
The following table contains all Aveknow of 
the composition of crops; you see that there is 
water in all this food. Wheat contains 15 
per cent of water, the turnip from 88 to 90 
per cent—showing the difference between 
grain and roots. The next column repre¬ 
sents the Avoody fibre which animals cannot 
digest, and in Avhich there is no nourishment. 
This in wheat and other grains varies from 
10 to 20 per cent. Here are starch and su¬ 
gar. Wheat contains about 55 per cent of 
starch; and here I must speak of this sub¬ 
stance, for it affords us an exceedingly beau¬ 
tiful illustration of the relations of the plant 
to the animal, especially to the life of the 
animal, and again of the animal to the life 
of the plant. About half the Aveight of 
Avheat consists of starch. 
So with barley, Indian corn, rice, peas and 
beans. Then all grains contain a substance 
analogous to gluten, but varying in this, that 
all do not contain the same quantity. Of 
this gluten, there exists in flour from 10 to 
19 per cent, in barley from 12 to 15, in oats 
from 14 to 19, in rye 15, in Indian corn 12, 
in rice 8, in buckwheat 8, in beans and peas 
from 24 to 28, Avhich is much more than is 
contained in any of the grains, and hence 
these produce the greatest effect upon cer¬ 
tain functions of animal life. In the potato 
and the turnip it isA^ery small, fornine-tenths 
of the turnip consists of water. Pea straAv 
is very rich in it; all other straws are com¬ 
paratively poor. Wheat and barley have 
little oil, oats from 5 to 7 per cent, Indian 
corn 5 to 9, beans and peas from 2 to 3 per 
cent Therefore these latter are deficient 
in oil. You find, going down, the quantity 
is small in the roots. So Avith the straws. 
they contain but httle oil. Prof. J. here 
pointed to a diagram, showing the quantity 
of saline matter in the ash of different straws. 
Now there are two things of which I must 
remind you: 1st, that of all these different 
kinds and forms of matter which exist in all 
plants, but in different proportions, gluten, 
starch and oil are largest in the grains.— 
Starch is the largest in the grains, gluten 
larger in the grains than in the straws, ex¬ 
cept pea straw, and is largest of all in the 
beans and peas. Oil or fat is greater in the 
seeds, and especially certain seeds cultiva- 
ed for food, greater in the oat and Indian 
tcorn than in other plants. Linseed I shall 
speak of, though this is cultivated for the 
oil and not for food, yielding about 60 per 
cent of it. Now these substances exist in all 
foods in different quantities. But how are 
these substances formed in the plant ? where 
does the plant get them ? This inquiry ren¬ 
ders it necessary for me to make you ac¬ 
quainted with a principle of great importance 
to a clear understanding of the relations of 
different kinds of animated nature, one to 
another, the relations of the plant to the soil 
and of the soil to the animal. Time Avill not 
permit me to introduce some interesting sub¬ 
stances existing in the soil from which plants 
are enabled to build up these kinds of food. 
But I will remind you, by way of illustra¬ 
tion, of an experiment made at our last meet¬ 
ing. I took a little limestone and poured on 
it a quantity of acid; I now repeat that ex¬ 
periment. The effervescence is owing to 
the evolution of a kind of air called carbonic 
acid gas, one property of which was that it 
extinguished a taper Avhen put in it; anoth¬ 
er was, that it could be poured out from one 
vessel into another; it is called acid, because 
in reality it is sour to the taste. This car¬ 
bonic acid consists of two of the elementary 
substances of which I have spoken, carbon 
and oxygen. This carbon exists in plants 
and forms a large portion of the wood, as 
the gluten and starch and fat do, of the seed. 
Table showing ike average composition of 100 
parts of the more common grains, roots, and 
grasses, 4*c. 
3 3 “ 
" ^ V- P 
o 
iO ^ Vx >0 to CO )-* ^ 
Cl o o ot in o to CO to ►u H- CO C5 o o Cl I 
^ ^ jS « .-5 JO 
o io w to w w w H.* o bi c /1 o ro i 
10400 .^. 1 - 1 ^ 041.0010 
Some of the above numbers, are approximations, 
only, especially the fatty matter, -which is very un¬ 
certain, and the buckwheat. 
Perhaps you Avill recollect that I explain¬ 
ed the structure of the leaves of plants, and 
shoAved how the under side, particularly, 
was studded with numerous pores or aper¬ 
tures, through Avhich the plant sucked in 
certain substances from the air. I told you 
at our last meeting, that the leaves of plants, 
spreatling through the air and exposing the 
large surfaces to it, sucked in this carbonic 
acid gas, Avhich exists in the atmosphere in 
a very small proportion. This table, (point¬ 
ing to a diagram) represents the proportion 
of carbonic acid gas Avhich exists in the at¬ 
mosphere. You Avill see that but one gal¬ 
lon of this ail- exists in 2,500 gallons of at¬ 
mospheric air. The leaves of plants, thro’ 
these little pores, suck out this gas from the 
atmosphere, in order that after undergoing 
certain chemical changes, it may serve to 
build up the substance of the plant. 
What are these chemical changes ? The 
plant sucks in the carbon as long as the sun 
shines. This carbonic acid gas consists of 
carbon and oxygen, and the plant sucks it 
in while the sun shines; but the leaves, at 
the same time that they suck in the carbonic 
acid, discharge very nearly as much oxygen 
as they take in of oxygen in the form of car¬ 
bonic acid; that is, if the leaf sucks in a giv- 
* For an analysis of Indian corn, by J. H. Salis¬ 
bury, see Transactions of 1848, p. 678. 
en volume of the two gases combined, it 
discharges the Avhole of the oxygen which 
it contains, and retains the carbon; there¬ 
fore, the function of the leaf is to suck in 
carbonic acid and throw off oxygen; to re¬ 
tain the carbon and throw off the oxygen. 
But it retains the carbon, not as charcoal; 
on the contrary, the plant exhibits green 
leaves, having no appearance of charcoal 
about them. But it undergoes certain chem¬ 
ical changes, the result of Avhich is, that the 
oxygen is given off, and the carbon becomes 
a neAV substance. That is one source from 
Avhich the plant derives the food, out of 
which the different substances in the table 
are formed. 
This illustration of the way in which leaves 
take in sustenance from the atmosphere, 
shows you the mode in which plants through 
the roots, as well as leaves, take in their 
food and convert it into another form of 
matter, the result being a change of Avhat 
is thus taken in, into starch, gluten and fat, 
which are found in all plants, and which are 
important to the nourishment of animals. 
I shall not dAvell on this noAv, but come 
back to it before I conclude. Having made 
you acquainted with the fact, as far as ne¬ 
cessary, to enable you to understand the 
general principle I Avish to fix on your minds, 
in regard to the composition of plants, I 
now draw your attention to the composition 
of animals. 
If I take any portion of an animal, for in¬ 
stance, the end of one of my fingers, and 
burn it, a large portion Avill burn aAvay, and 
there would remain behind, also a large por¬ 
tion. The larger portion of the finger, the 
bone, would remain, in fact, being nearly 
the whole of the original bulk. So, if I take 
a piece of flesh, and cut off a bit of this mus¬ 
cle, excluding both the fat and the bone, and 
burn it, I find that a large portion burns 
away; but there remains a quantity of ash. 
Here we find precisely what Ave find in burn¬ 
ing the plant Every part of the plant 
which burns, leaves behind it, a mineral 
matter or ash. So it was with the soil, and 
so we find it noAV with the animal. These 
general relations betAveen the soil, the plant 
and animal, all resolve themselves into the 
fact, that all of them consist of a part which 
burns aAvay, and a part which does not; of 
the soil, the part that burns away is small; 
in the plant, it is very large; but in animals, 
we find both of these conditions; the soft 
parts of the animal, bear a similarity to the 
plant, in that the quantity which burns away 
is greater than Avhat is left; but if you burn 
the bone, there will remain a large quantity 
of mineral matter—the ash of the bone is 
greater than what biurns away. Thus a 
quantity of mineral matter is left by every 
part of the animal which is burnt, and the 
quantity varies Avith the part of the animal 
Avhich Ave burn. But I do not dwell on the 
mineral substance left. I draw your atten¬ 
tion to the organic part that burns aAvay.— 
Look at this piece of beef. Here are three 
different substances; the muscle, or red part, 
the fat, and the bone. Now, in every part 
of the animal, leaving out the viscera, you 
find these three forms of matter exist; the 
fat, the muscle, and the bone. 
Consider these different substances. The 
fat has a strong analogy to the fat existing 
in plants. If I take a portion of the fat— 
the suet as it is called—and put it under a 
press, I can squeeze out oil, which shows 
that in this sohd fat, liquid fat is present— 
From this candles may be made, soap, (fee. 
I have said that this is analogous to the fat 
in plants. Take ohve oil, for instance; in 
Avinter, it becomes a solid lump of fat, but 
put it under a press and you can squeeze 
out an oil that would not freeze, and it will 
leave a substance that is oily, and that will 
remain solid even in summer. Here you 
see the analogy between the fat of plants 
and that of animals. The solid fat of olive 
oil is the same as the solid fat of animals. 
If I eat olive oil, I eat solid fat, precisely 
hke that of my OAvn body. But I pass over 
this, believing that you will concede to be 
true what I cannot explain further—that the 
fat of all animals has a relation to the fat of 
all plants. 
Noav take this muscle, colored by blood; 
cut it out and Avash it with water, until you 
Avash out all the blood, you get a perfectly 
white substance, Avhich can be draAvn or 
torn into fibres. This is called fibrin. Now 
this fibrin is almost identical with the gluten 
of plants. Hero then, is another analogy 
betAveen the plant and the animal. There¬ 
fore, as the iat of animals is found to be 
identical Avith that of plants, so the muscle 
of animals is almost identiciil Avith that part 
of the plant called gluten. 
But how with the bone ? In plants there 
are no bones, Ave have hard substance, which 
is not bone but Avhich is sometimes very 
hard, as the Avood of ebony. Burn the wood 
of plants and you have a small quantity of 
ash; burn the bone of animals and you have 
a large quantity. In tracing out the analo¬ 
gy betAveen plants and animals, let me draw 
your attention to the bones of animals.— 
Here is the bone of the ox; the cartilege 
will burn aAvay, one third of the dry bone 
Avill burn aAvay. Noav of the phosphate of 
lime 57 per cent exists in the bone —phos¬ 
phate of lime consists of phosphoric acid 
and lime. You recollect, I told you that 
phosphoric acid and lime both exist in plants 
—and in the ash of the grain of wheat, to 
an amount equal to one half of the whole 
bulk. You see therefore that we have in 
the bone and the ash of the bone, those sub¬ 
stances which seem to form the largest pro¬ 
portion of the mineral matter existing in the 
different kinds of food that we eat, and also 
in the food for cattle. Where does the an¬ 
imal get these substances forming the dif¬ 
ferent parts of the body—the muscle, the fat 
and the bone ? It is obtained from the food 
which is eaten; but observe, that Avhile the 
plant draws from the soil and the air, one 
form of matter, and converts it into another, 
as for instance, carbonic acid gas—does the 
animal do it ? No: on the other hand, the 
animal takes in, not the raAv material, as it 
were, but the material already produced by 
the plant—the animal takes in this gluten, 
in the form of bread or grain, which gluten 
is almost identical with the solid part of the 
muscle. The animal also takes in fat with 
its food. Whether we eat vegetable or an¬ 
imal food, we take in fat substances closely 
related to the fat of our own bodies; and in 
regard to the bone, we take in food that 
contains the material which forms the min¬ 
eral matter of the bone itself. Therefore, 
though the plant bears this relation to the 
animal, the plant could exist without the an¬ 
imal, but not the animal without the plant 
The animal could not suck in the atmos¬ 
phere and convert that into the solid parts 
of its own body—it is so ordered that the 
plant drinks in from the air certain sub¬ 
stances, and certain other substances from 
the soil, which are necessary to its growth, 
just as we would take a purse from the 
pocket and select a piece of money taking 
out of both, what it wants, and nothing more. 
So when food is introduced into the stomach, 
it is immediately placed in contract with the 
digestive organs, which perform the same 
office for the body, as the leaves do for the 
plant The stomach has its pecular func¬ 
tions and selects from the material that the 
plant has prepard, the very things Avhich 
are needed to biiild up the several parts of 
the body, which require to be built up.— 
But there is a difference which I must ex¬ 
plain ; I have shoAvn a strong analogy be¬ 
tween the plant and the animal, we have 
seen that both contain fat and gluten. But 
I said I would draw your attention more 
particularly to these substances. Starch, 
we find, exists in Avheat, to the extent of half 
the Aveight of the grain, and we eat Avith our 
food, a large quantity of starch. Is there 
any starch in the human body ? No! Here 
then is the striking difference to which I 
have alluded. We find that in this food, 
Avhich is supposed to be especially made to 
sustain the human family, viz: the grains, 
we find starch forms nearly half of the whole 
bulk. What is the end or purpose of this ? 
To understand this, it is necessary to explain 
one or two functions of the animal. 
Living animals perform various functions. 
The food they eat is digested; that is the 
most important function; but Ave cannot 
compare the importance of one function with 
another, in the living animal; for if any one 
function ceases to be carried on, the animal 
ceases to live. But what is the distinction ? 
First of all, the food is dissolved in the 
stomach, and by means, of the organization 
of the stomach, the ifoimal selects from it, 
the materials necessary for such parts as 
need it. But the animal breathes. Stop 
our breath, and we could not live a moment 
What is the effect on animal life, of breath¬ 
ing ? Here is the difference between plants 
and animals. Compare the composition of 
air, before it goes into the lungs, with its 
composition, when it comes out; you Avill 
find that the air comes out, charged with a 
greater quantity of carbonic acid gas, than 
when it went in. In its passage through 
the lungs, the volume of this gas is greatly 
increased. This carbonic acid comes from 
the blood of the system; it consists of car¬ 
bon and oxygen, and is obtained from the 
food. The animal, in fact, draws in air, and 
throws out air of a different composition; 
the oxygen is diminished, and the carbon in¬ 
creased. 
Of what does starch consist ? Of carbon 
in large quantities. When the leaves draw 
in carbonic acid they throAV off’ oxygen; the 
carbon only remains, and that in a new state 
of combination; it forms starch among other 
things, by uniting Avith water—starch in fact 
consists of Ctxrbon and water only—so that 
in forming starch the carbonic acid unites 
Avith Avater in the plant. It forms starch, 
Avhich the sap of the plant conveys to the 
part which requires it. We find it largely 
in the ^eeds. Now, the function of the leaf 
is to change this carbonic acid and form 
starch. The animal takes this starch into 
the stomach and decomposes it, and it es¬ 
capes from the lungs in the state of carbon¬ 
ic acid and water. I say Avater, for if I take 
a clear, dry glass and breathe into it, it 
makes it opaque; the moisture of the breath 
being condensed upon the cool glass. The 
lungs, therefore, are continually throAving oft’ 
carbonic acid and water, and these are throAvn 
oft' at the expense of the food .which the an¬ 
imal eats; that is, the starch Avhich is con¬ 
veyed into the stomach in the form of food, 
is by certain jmimal processes, converted m- 
to carbonic acid and water and thrown off 
by the lungs. If I take a piece of starch 
and kindle it, it Avill burn much like wood, 
and give out heat and light; and when it 
gives out this heat and light it is converted 
into carbonic acid and water, or into the same 
things exactly as it is by the respiration of 
the animal. Thus the functions of animal 
life convert starch into the same substances 
as when we bum it 
You wiU ask, what is the purpose of all 
tliis ? The plant sucks in carbon and wa¬ 
ter, and the animal takes it in in the shape 
of food and discharges it again in the same 
form. Is this designed for the mere amuse¬ 
ment of the animal? No; the purpose is 
this: animals require to be kept warm, and 
among the means to keep up warmth one 
is the application of external heat It is al¬ 
so kept warm by its food. The animal 
that is stationary will keep itself above 
the temperature of the air without the 
appUcation of heat, because the animal 
has Avithin itself a source of heat; and 
just as Avhen starch is burned it gives out 
heat, so in the interior of the body—though 
it does not burn as rapidly, and gives no 
light—yet it undergoes a slow chemical 
change, which is known to produce heat, 
that keeps the body warm, and thus starch 
serves to keep up the animal heat. That, 
at least, is the present opinion. The animal 
takes in this starch with its food, the plant 
mixes it. up Avith what the animal eats. The 
animal must eat starch with other substan¬ 
ces, and thus the animal cannot eat what 
will not supply the materials to enable it to 
discharge all the functions of the body. Na¬ 
ture mixes up these things in order that 
respiration may go on and that the animal 
may be kept warm, and provides also that 
the plant may undo what the animal has 
done, and thus renew the substances neces¬ 
sary to keep up the animal functions. 
You cannot fail to see how very beauti¬ 
ful this cycle is. Here is a continual opera¬ 
tion going on, by Avhich the carbonic acid 
and water of the atmosphere are converted 
by the plant into food, one of the component 
parts of which is starch, and by Avhich it is 
again returned to the atmosphere, in the 
state of the same carbonic acid and water. 
But there are larger cycles than this, on 
which the existence of animal life depends. 
To advance one step fimther: You see 
noAv the reason why it is that the plant dif¬ 
fers from the animal, in that it contains this 
large quantity of starch. But what is the 
relation of other kinds of food that the plant 
conttiins, to the animal ? What is the func¬ 
tion of gluten, or that substance which we 
have found to be nearly identical with the 
fibre of the muscle ? When the animal eats 
vegetable food, it eats a portion of this ma¬ 
terial, Avhich is so nearly identical with its 
own muscle. You understand, no doubt, 
that if certain parts of the animal are build¬ 
ing up or increasing, why it is necessary to 
give it continued supplies of that substance, 
from Avhich the muscle is built up. If this 
is Avhat supplies the growth of muscle, you 
might say that if the muscle is fully formed 
it is not necessary to keep it up; that if this 
substance is introduced into the stomach, 
and the gluten is selected Avhich goes to 
form the muscle, that the gluten, in such a 
case, is not Avanted. But tliis is not so; this 
laAV exists, though the body may appear to 
be identically the same, yet it is continually 
changing and undergoing renovation in dif¬ 
ferent parts. There are certain parts, of 
every portion of every animal, removed eve¬ 
ry day, and a quantity of new material put 
in its place, so that the body is kept up by 
the continual addition of new matter. 
The way this takes place may be thus il¬ 
lustrated : Suppose you have a scar that has 
remained as far back as you can recollect; 
if the doctrine be true, that the whole body 
is renewed once in five years, you may well 
think it curious that this little mark should 
remain so long, Avithout any apparent change 
in its appearance; but it is in fact, engraved 
as it were, not on the matter originally in¬ 
jured, but on other matter. You can un¬ 
derstand this, by this simple illustration:— 
Suppose this building to be of brick, and 
that every day some small part of it is taken 
out, a brick from this or that place and a 
new one put in, until the Avhole building has 
been renewed, and yet no apparent change' 
in it beyond the color of the neAv material;' 
for you can conceive Iioav such a process 
might go on, until every part of the build¬ 
ing had been replaced by other materials; 
and yet the building remains a complete 
building in all its parts, its interior accom¬ 
modations and its outward proportions. Tliis 
is constantly taking place in your body; from 
every part of it a portion is removed every 
day, more or less, according to the quantity 
of material taken in, in the shape of food. 
Hence, the animal should have a constant 
supply, in order that this dmly Avaste may 
be made up. An animal requires to sus¬ 
tain, its body in good condition, or to supply 
Avhat is called the sustaining food, about 
one-sixtieth part of its OAvn Aveight, and to 
keep it in condition, one-fiftieth or one-six¬ 
tieth part of its own weight, every day, to 
sustain its daily waste. 
If you Avant to give it food, to increase its 
size, to enable it to do Avork, or to produce 
milk, then you must give it more food. If 
you feed it for milk you must give it twice 
that quantity. You must adapt your food 
to the points for Avhich the animal is fed; and 
you can do this, for the art of feeding ani¬ 
mals with a view to certain results, is one qf 
those arts which science has given to the 
fiirmer. If I want to lay on muscle, I must 
