LIFE. 151 
soon as the living body has begun to change the 
composition of the substances upon which it 
acts, it endows them with a new set of affinities, 
contrary to those which it before possessed 
when subject to the operations of chemistry. 
Others, again, are content to refer the opera¬ 
tions in question at once to the ever-ready vital 
principle, which, according to them, produces 
and directs these changes in the organism, and, 
so long as it resides there, keeps in check the 
natural tendency of its structure to decay. We 
are inclined to believe, on the other hand, that 
the operations in question are immediately due 
to the agency of the same laws as those which 
preside over inorganic matter, operating, how¬ 
ever, under conditions which the living or¬ 
ganism alone can supply. We shall now 
examine what evidence may be produced in 
favour of this opinion, and how far it is con¬ 
sistent with the general phenomena of life. 
V. Changes in composition.—The ali¬ 
mentary materials which serve as the food of 
the living organism, cannot be appropriated by 
its several tissues, and rendered like themselves 
in structure and properties, until they have un¬ 
dergone certain changes in composition, by 
which the proximate principles are produced. 
It is by the organisation of these compounds, 
that the constant disintegration of the elemen- 
tary parts of the living system is compensated, 
and those vital properties maintained, the exer¬ 
cise of which forms an essential part of the 
circle of actions involved in life. Another 
class of changes in composition consists in the 
production, from the same materials, of the 
peculiar ingredients which characterise each se¬ 
creted product ; some of these may be regarded 
as directly eliminated from the nutritious in¬ 
gredients of the blood, in the same manner as 
are the solid tissues themselves ; whilst others 
would rather seem to resuk from the new com¬ 
bination of the disintegrated elements, which 
are taken up and removed by the current of the 
circulation, and carried to organs destined to 
separate them entirely from the living portions 
of the system. All these changes are frequently 
said to be effected by a vital chemistry ; or (to 
speak in more precise language) to result from 
the operation of vital affinities, of a different 
character from those ordinary chemical affinities 
which produce the well-known changes in the 
inorganic world. In conformity with the New¬ 
tonian direction to avoid unnecessarily multi¬ 
plying causes, we shall briefly examine the 
grounds upon which this hypothesis is based, 
and enquire whether it is requisite for the ex¬ 
planation of phenomena, or even gives us any 
assistance in our researches. 
The chief ground for the assumption of a 
distinct set of vital affinities appears to be, 
that the mode of union of the elements of the 
organic compounds is essentially different from 
that which prevails in the inorganic world ; 
and that the chemist, who has the power of 
effecting or controlling those changes which are 
produced by physical laws, and can therefore 
imitate to a great extent the immense variety of 
combinations which the mineral kingdom af¬ 
fords, is unable to effect or control the action of 
similar materials, so as to produce any of the 
class of organic compounds or proximate prin¬ 
ciples. It has, until very recently, been re¬ 
garded as a distinctive character of organic 
compounds, that their elements are combined 
in ternary or quaternary arrangements of com¬ 
plex nature, in which each ingredient is equally 
united with all the rest; whilst all inorganic 
substances admit of being ultimately resolved 
into simple binary combinations. Thusfibrin 
is regarded as composed of 6 parts of carbon, 
2 of oxygen, 5 of hydrogen, and 1 of nitrogen ; 
and these elements are imagined to form a qua¬ 
ternary compound, all having a mutual attraction 
for each other ; whilst carbonate of ammonia, 
which consists of 1 carbon, 2 oxygen, 3 hy¬ 
drogen, and 1 nitrogen, is a binary combination 
of two other binary compounds, carbonic acid 
and ammonia. But on this it may be remarked, 
that there are undoubtedly some proximate 
principles, (that is to say, the simplest forms to 
which organic compounds can be reduced, 
without altogether disuniting them into their 
ultimate elements,) which consist of two ele¬ 
ments alone, and which exist in this simple 
form in living bodies. Such are some of the 
compounds of carbon and hydrogen. Further, 
the rapid progress of analytic research is leading 
to the belief that the complex arrangements 
just referred to may be resolved into those of a 
binary character; so that most organic com¬ 
pounds may be regarded as resulting from the 
union of others of simpler nature, just as a salt 
is formed by the union of an acid and an alkali. 
The discovery of cyanogen, and of its capabi¬ 
lity of acting as a compound radical,—uniting, 
like chlorine or iodine, with hydrogen to form 
an acid, and even occasionally serving, like 
oxygen or sulphur, in combination with some 
metals, as the base or alkali to such an acid,— 
was the first step in a career of brilliant disco¬ 
veries, which, even at the present day, may be 
regarded as scarcely commenced. When cy¬ 
anogen combines with a metal, the combination 
is in reality a ternary one, although in all its 
properties it has a binary character. Thus, the 
cyanuret of silver (whose ultimate composition 
is 1 part of the metal, with 2 carbon, and 1 
nitrogen,) will form a salt, in which it acts as 
the acid or negative ingredient, with the cya¬ 
nuret of potassium; and the soluble cyanurets 
will form salts with the chlorides or iodides of 
the metals, thus establishing their claim to a 
binary character. But still further;—cyanogen 
in combination with iron appears itself to act 
as a compound radical, combining as a simple 
body with other elementary substances* From 
the analogy afforded by this and other in¬ 
stances, many chemists are now disposed to 
look upon the combination of the oxy-salts in 
a new light. It is suspected that, when sul¬ 
phuric acid and soda are brought together, the 
resulting compound is not formed by the union 
of an atom of the acid with an atom of the 
alkali, but by the generation of a new com¬ 
pound radical, sulphatoxygen, consisting of 1 
part of sulphur with 4 of oxygen, which unites 
* Liebig, in Turner’sLffiemistry, 6th ed. p. 77g.