William Prout (1785-1850)

On the ultimate composition of simple alimentary substances; with some preliminary remarks on the analysis of organised bodies in general

Philosophical Transactions of the Royal Society 355 (1827) [as excerpted in Mikulás Teich, A Documentary History of Biochemistry, 1770-1940 (Rutherford, NJ: Fairleigh Dickinson University Press, 1992)]


Organic chemistry is confessedly one of the most difficult departments of the science; and though much has been done, and more attempted on the subject, it is yet in a very imperfect and unsatisfactory state; and it must be frankly admitted that Physiology and Pathology have derived less advantage from this most promising and really powerful of the auxiliary sciences, than might have been expected. To explain this perhaps would not be difficult; but as the explanation would be misplaced here, I shall merely observe, that dissatisfied with the old modes of inquiry, I determined to attempt a different one, and keeping in view the notions I had originally formed respecting chemical combinations, proposed to myself to investigate the modes in which the three or four elementary substances entering into the composition of organized bodies are associated, so as to constitute the infinite variety occurring in nature.

With these views my first object was to determine the exact composition of the most simple and best defined organic compounds, such as sugar, and the vegetable acids, a point that had been several times before attempted, but, as it appeared to me, without complete success. About the same time also albumen and other animal products, as urea, lithic acid, &c. were examined with similar views. The subject of digestion, however, had for a long time occupied my particular attention: and by degrees I had come to the conclusion, that the principal alimentary matters employed by man, and the more perfect animals, might be reduced to three great classes, namely, the saccharine, the oily, and the albuminous: hence, it was determined to investigate these in the first place, and their exact composition being ascertained, to inquire afterwards into the changes induced in them by the action of the stomach and other organs during the subsequent processes of assimilation.


It has been known from the very infancy of chemistry, that all organised bodies, besides the elements of which they are essentially composed, contain minute quantities of different foreign bodies, such as the earthy and alkaline salts, iron, &c. These have been usually considered as mere mechanical mixtures accidentally present; but I can by no means subscribe to this opinion. Indeed, much attention to this subject for many years past has satisfied me that they perform the most important functions; in short, that organization cannot take place without them. This point will be more fully investigated hereafter: at present it is sufficient merely to observe, that many of those remarkable changes which crystallized bodies undergo on becoming organized, are more apparent than real; that is to say, their chemical composition frequently remains essentially the same; and the only points of difference that can be traced, is the presence of a little more or less of water, or the intimate mixture of a minute portion of some foreign fixed body. There is no term at present employed which expresses this condition of bodies, and hence, to avoid circumlocution, I have provisionally adopted the term[1] merorganized, (μεξοσ [sic, although μερος appears more likely.--CJG] pars vel partim) meaning to imply by it that bodies on passing into this state become partly or to a certain extent, organized. Thus starch I consider as merorganized sugar, the two substances having, as we shall see presently, the same essential composition, but the starch differing from the sugar by containing minute portions of other matters, which we may presume, prevent its constituent particles from arranging themselves in the crystalline form, and thus cause it to assume totally different sensible properties.[2]

[1]I am indebted to my friend Mr Lunn for this term.

[2]When this subject first occupied my attention many years ago, I was at a loss to form any notion of the modus operandi of these minute admixtures of foreign bodies, except the mechanical one mentioned in the text, viz. that they operated by being interposed, as it were, among the essential elements of bodies, and thus by weakening or modifying their natural affinities. But the admirable Paper, published by Mr Herschel, in the Philosophical Transactions for 1824, 'On certain motions produced in fluid conductors when transmitting the electrical current', appeared to throw an entire new light on the subject. The facts brought forward in this Paper are of the most important kind, and seem to be evidently connected with a principle of a more general character, which when completely developed, will lead to the most unexpected results. 'That such minute proportions of extraneous matter,' says Mr H. 'should be found capable of communicating sensible mechanical motions and properties of a definite character to the body they are mixed with, is perhaps one of the most extraordinary facts that has yet appeared in chemistry. When we see energies so intense exerted by the ordinary forms of matter, we may reasonably ask what evidence we have for the imponderability of any of the powerful agents to which so large a part of the activity of material bodies seem to belong?'

Any substance may be supposed capable of performing the part of a merorganizing body; but, in a certain point of view, water appears to constitute the first and chief, at least in organized substances.

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