September 3, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
183 
It is not my intention to enter into controversy, 
and I shall consider my object attained if the follow¬ 
ing remarks should contribute something towards 
throwing light upon the conditions that have to be 
ascertained in regard to this question. 
Scientific men are tolerably clear in their views as 
to the mode in which oxygen operates in the animal 
body: oxygen combines with the elements of the food 
or of the body, carbonic acid, water and urea being 
regarded as the ultimate products of the combustion. 
In consequence of that combustion heat is pro¬ 
duced, which warms the body and maintains its 
temperature, or becomes sensible in the form of me¬ 
chanical effect. 
If the heat of combustion proper to the various 
kinds of food be known, it would express for each, in 
some sort, its value as a source of power. 
“ From this point of view,” says Frankland, “ it is 
Interesting to examine the various articles of food in 
common use, as to their capabilities for the production 
of muscular power,” and by the determination of the 
heat of combustion proper to each, he arrives at the 
result that, for equal weights of food materials in 
the natural condition, Cheshire cheese represents 
three times as much force, expressed in food-pounds, 
as lean oxflesli; sugar two and a half times as 
much ; and butter five times as much. 
Here it is throughout assumed that muscular 
power is generated by the combustion of these mate¬ 
rials in the muscles, and that the process of combus¬ 
tion is like that taking place under the boiler of a 
steam-engine. In this respect, we find two parts by 
weight of dry potatoes put down as equal to one and 
a half parts of dry flesh and to two parts of boiled 
ham (dry), etc. These are certainly most interesting 
results; in any case they are very unexpected re¬ 
sults of the theory. 
This is, perhaps, the place to call to mind that the 
combination of combustible elements of the animal 
body with oxygen is a process of a totally different 
nature from the ordinary process of combustion. 
Carbonic acid is never produced in the animal body 
by the combination of oxygen with carbon; it is not 
a product of combustion in the ordinary sense of that 
term.* 
In order to comprehend correctly the difference 
between the process of combustion under a steam- 
boiler and that in the animal body, it is necessary to 
consider how the formation of organic compounds in 
plants takes place. These compounds are all formed 
out of carbonic acid; they represent carbonic acid 
.atoms that have been more or less altered. In the 
animal body those compounds are again converted 
into carbonic acid, or into what they originally were. 
In the formation of these compounds under the 
influence of sunlight, there is an absorption of heat 
or sun force. This becomes latent, and in the re¬ 
conversion of those compounds into carbonic acid 
that heat is again liberated. This liberation of heat 
is at the maximum when the reconversion of the 
.compounds into carbonic acid corresponds exactly to 
their formation. 
For example, comparing carbonic acid with sugar 
in their most simple empirical formulae, we have— 
r O r H 
°0 °0 
Carbonic acid. Grape sugar. 
A glance at both formulse shows that sugar is, in 
* See “ The Chemical Process of Respiration,” Ann. Chem. 
IHiarm. lviii. 335. 
fact, carbonic acid in which one equivalent of oxy¬ 
gen has been replaced by hydrogen. Carbonic acid 
is not decomposed in the formation of sugar, but it 
is only altered by the exchange of one of its consti¬ 
tuents for sometliing else. 
In the conversion of sugar into carbonic acid, it is 
not the carbon of the sugar that is burnt, but the 
hydrogen that had been introduced by substitution 
into the carbonic acid. When this hydrogen com¬ 
bines with oxygen in the animal body and forms 
water, its place is again taken by oxygen which had 
been eliminated from the plant. Consequently, 
sugar can be burnt in two ways and converted into 
carbonic acid,—either directly, by combination with 
oxygen at a high temperature, or indirectly, by the 
replacement of its hydrogen by oxygen at a moderate 
temperature. The proportion of oxygen is, in both 
cases, the same,—sixteen parts by weight for every 
fifteen parts of sugar; but if there be inequality in 
the work of combustion, by which heat is expended, 
the heat liberated must also be unequal. 
I will continue the exposition of this case, though 
without assigning any weight to the accuracy of it; 
my object is merely to show the difference which it 
is the business of the physicist to elucidate more 
completely. 
If we suppose that, with the above-mentioned for¬ 
mula for grape-sugar, G grams of the carbon in 15 
grams of sugar combine with oxygen directly, then 
there would be 6x7838 unit3 of heat developed. 
But if we suppose that 1 gram of hydrogen were 
oxidized by 8 grams of oxygen, and that the 8 grams 
of oxygen introduced were to generate with the rest 
of the carbonic acid=14 grams carbonic oxide, just 
as much heat as in its combination with carbonic 
oxide, we should then have,— 
In the first case 47,000 units of heat* 
„ other „ 68,900 ,, „ 
Therefore in the latter 21,900 ,, ,, more. 
It may be shown by undoubted facts that differ¬ 
ences of tills kind do really occur in the quantities of 
heat generated by combustion. 
Frankland determined among other things the 
heat of combustion of cane-sugar, and found that 
1 gram gave 3348 units of heat. Hence it follows 
that 171 grams of cane-sugar (1 atom) would give 
572,508 units. 
In fermentation there are produced from sugar 
carbonic acid and alcohol, and, if no other products 
were formed, 92 grams of alcohol should be obtained 
from 171 grams of sugar; in reality, only 88 or 89 
grams are obtained,—let us say 88£; the deficiency 
is succinic acid and glycerine, etc. 
According to numerous determinations by exact 
observers,—Dulong, Despretz and Favre,—1 gram 
of alcohol yields as the mean 6981 units of heat, and 
88| grams would give 617,818 units. 
Consequently, alcohol itself gives, when burnt, 
45,310 units of heat more than the corresponding 
quantity of sugar by the decomposition of which it 
has been formed. To this must be added the heat 
generated in the fermentation of sugar; according 
to the direct determination of Dubrunfaut, this 
amounts to one-eighth of the heat that would be ge¬ 
nerated by combustion of the carb on contained in 
Heat units. 
* By combustion of the hydrogen ..... 34,533 
By combination of 14 grams carbonic oxide 
with 8 grams oxygen. 34,384 
Total.68,917 
