October 1, 1870.3 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
261 
THE PROCESS OF NUTRITION. 
BY BARON LIEBIG. 
The achievements of that art which relates to the 
preparation of food are really surprising in regard to 
the economy of power and the increased efficacy of 
food materials within a given time. Under the in¬ 
fluence of heat, as already mentioned, the digesti¬ 
bility of the chief constituents of food is rather aug¬ 
mented than diminished. The operations of roasting 
and boiling, the long-continued simmering practised 
in the preparation of various kinds of flesh, either of 
mammalia, fish, or birds, the selection of vegetables 
and sauces to accompany particular dishes, are all 
means calculated for effecting the disintegration of 
the food or complementing and increasing its action, 
as well as for shortening the time required for the 
work of digestion. With the cliild we find a differ¬ 
ence even with sugar and milk-sugar, while both are 
preferable to starch. 
Experienced cooks attach the greatest value to the 
soluble constituents of the muscles of mammalia as 
an adjunct to their viands. To obtain this working 
material of muscle, they prepare from the waste frag¬ 
ments of the kitchen an extract, the importance of 
which is characterized by its name, “ stock,” which 
is understood to denote its applicability as a basis or 
for enriching other preparations of food. 
It is wholly unintelligible that the dietetic value 
of the extractive material of flesh should not have 
been recognized long ago and regarded as perfectly 
well established; it is equally unintelligible that 
doubts should still exist in regard to it even among 
physicians, while the efficacy of this material hi the 
form of broth for promoting the strength of conva¬ 
lescents has been well known, not only for years, but 
since the time of Hippocrates. 
It is clear that this material, taken in the form of 
soup or sauces, or as an adjunct to vegetable food, 
must have the same effects on the annual body as 
when it is taken as a part of meat. 
In regard to the selection of food corresponding to 
the wants of man, instinct is an infallible guide, 
when aided by that watchman of health, the sense 
of taste; it may be misled for a time, but not perma¬ 
nently. At the entrances of the Munich beer-cellars 
we find a law of nature expressed by the proximity 
of the never-failing cheese-booth. The beer-drinker 
consumes his respiratory material in the form of beer, 
w hil e in the form of cheese he obtains the material 
indispensable for production of blood and for gene¬ 
rating force. Since beer serves as respiratory ma¬ 
terial more readily than fat would do, he dislikes fat 
and declares it to be unwholesome. With the beer 
lie eats his cheese without butter. 
The extractive substances of flesh when added to 
food do duty as true nutritive materials in the place 
of those substances which are otherwise produced 
from albumen. The most simple observation will 
suffice to dispel any doubt of this. 
The experiments of Bisclioff and Voit have esta¬ 
blished the fact that gelatin has a considerable nu¬ 
tritive value when combined with meat—about one- 
fourtli that of albumen,—so that while a dog weigh¬ 
ing 36 kilograms lost in about four days one pound 
in body-weight when fed with 500 grams of meat 
alone, he gained in three days about 134 grams when 
the same quantity of meat was given together with 
200 grams of gelatin. 
According to our knowledge of the nature of gela- 
Third Series, No. 14. 
tin and its composition, this power of nutrition 
cannot be accounted for on the assumption that the 
gelatin, or any part of it, is converted into albumen, 
so as in this way to add to the quantity of albumen 
consumed ; but we must infer that it has this power, 
because it replaces certain substances necessary for 
the animal organism, which are produced more readily 
from gelatin than from albumen; so that, in conse¬ 
quence of this, the annual is relieved from work, to 
s ime extent, while a certain quantity of albumen 
remains available for other purposes. 
A dog may be fed with boiled porridge made of the 
entire grain when bone-meal is added to it, and 
the animal will thrive almost as well as if fed upon 
meat. 
I believe that the imperfect appreciation of laws of 
nutrition and dietetics is to be ascribed to two erro¬ 
neous ideas; one is that, in experiments on nutri¬ 
tion, a particular animal has been regarded as the 
representative of all animals, and it has been 
deemed proper to draw general conclusions as to the 
process of nutrition from experiments made with 
that particular animal alone. From observations on 
carnivorous animals inferences have been drawn as 
to the phenomena in herbivorous animals; and from 
the action of vegetable food in the body of a car¬ 
nivorous animal attempts have been made to draw 
conclusions as to the nutritive value of meat. 
The dissimilar expenditure of power in individuals 
of different classes of animals, or the generation of 
power for the performance of interior and exterior 
work, is but little regarded by some physiologists; 
with many, indeed, the animal body is nothing more 
than a machine that converts albumen into urea. _ 
A second equally great error consists in ascribing 
to albumen, as some physiologists do, an action 
which it does not at all possess, according to its na¬ 
ture. 
Albumen is, for the animal body, nothing more 
than what carbonic acid, water and ammonia are for 
plants ; and in this its value is sufficiently high. 
Besides the importance that water has for the plant, 
inasmuch as it yields hydrogen to it, there is another 
chemical value it has for the plant, in being the 
means by which carbonic acid is taken up, and by 
which mineral food is supplied. In like manner, 
carbonic acid, which yields carbon, has the particular 
virtue of rendering soluble several substances which, 
are insoluble in water. Albumen, also, possesses 
similar characters, but it does not exercise any spe¬ 
cial action; and it is a misconception of the nature 
of albumen to suppose that physiological phenomena 
are to be explained by means of the idea we have of 
albumen. It is only by means of the things pro¬ 
duced from albumen that this substance acts, and 
therefore it is impossible for me to concur in the 
modern notions of organized albumen and circulating 
albumen, which are, nevertheless, one and the same 
thing. These notions introduce confusion to such a 
degree that one does not know how to distinguish left 
from right. 
All combustible plastic constituents of the animal 
body are, in fact, altered atoms of albumen, just in 
the same way that the constituents of the plant are 
altered atoms of carbonic acid ; and it is quite certain 
that most of the products originating from albumen 
in the animal organism are capable, when taken as 
food, of replacing albumen in the processes of nutri¬ 
tion and force production, as well as in special pro¬ 
cesses, as is the case with sugar and fat, or their den* 
