446 
DR. PROUT ON CHEMISTRY. 
causes in the organic kingdom. In the inorganic kingdom, also, 
the primary compound in general, as in the instance of carbonate 
of lime, is fixed and definite in its nature, and thus easily sepa¬ 
rated from foreign bodies, and made to crystallize as we choose. 
But in the organic kingdom the case is very different: here the 
substances, though undoubtedly primarily composed according to 
precise chemical laws, are naturally so unstable in their condition, 
and so easily decomposed, that from this cause alone they can, 
in very few instances, be separated from the contaminating 
matters, and be obtained in a perfectly pure state. 
But it is well known, that the foreign bodies met with in 
organic products are more intimately mixed, and adhere with 
greater obstinacy to the primary elements, than similar sub¬ 
stances in inorganized bodies. They are also, for the most part, 
so uniform and constant in their character in the same substance, 
that, whatever office they may be supposed to perform, it is diffi¬ 
cult not to believe that it is a most important one, and quite as 
essential to the existence of the body in its organized condition as 
the elements of which it is chiefly composed. How these bodies 
operate is not so easy to explain. That they do not enter into the 
composition of organized bodies in definite proportions, according 
to any known chemical laws at least, is evident; and the only 
notion that, for a long time, I could form to myself on the sub¬ 
ject was, that they perform an office which may be termed inter¬ 
stitial —that is to say, that they operate by being interposed, as it 
were, between the essential elementary atoms of organized sub¬ 
stances, and thus prevent them from assuming the crystallized 
form, in which state they would be totally unfit for the purposes 
of the economy of living organized beings. 
This mechanical explanation of the operation of minute foreign 
bodies, though probably correct to a certain extent, or as far as it 
goes, is obviously, however, inadequate to explain all the pheno¬ 
mena. Whoever has carefully studied the effects of minute 
quantities of matter upon common chemical action, and infinitely 
more upon organic action, must be aware that they often appear 
to exert energies totally inexplicable upon any known principles. 
The subject, however, has by no means received the attention it 
deserves; and, indeed, besides myself, I do not know any one 
that has attended to it at all—at least in the point of view 
in which we are considering it here. There is, however, one very 
important series of experiments made by Mr. Herschel, and pub¬ 
lished in the Philosophical Transactions for 1824, which struck 
me at the time as remotely bearing on the subject; and though, 
in the present state of our knowledge, these experiments can be 
hardly so applied as to throw much immediate light on the sub- 
