These are among the remarkable instances of the catalytic action recently described by Berzelius,* which is common to organic and inorganic operations, and which is not yet found to be comprehensible within the known laws of chemical affinity. The peculiarity of the action consists in the production by one body, A, of a change in the composition of another, B C, without itself undergoing any alteration. Thus, the peroxide of hydrogen, which is readily decomposed by any substance having an affinity for oxygen, is also decom posed by some which themselves undergo no change, such as the metals and the fibrin of the blood ; these produce in it a state analogous to fermentation, oxygen escaping and water being left. Again, not only decompositions but new combinations may be effected in this manner. Thus, most metals at high temperatures, and platinum in a state of minute division at low temperatures, as well as various porous sub stances slightly heated, produce the union of oxygen and hydrogen in an explosive mixture. The action of sulphuric acid on alcohol in pro ducing ether, without itself undergoing change, appears referable to the same class along with those just described. We may consider it proved, then, that many substances possess the power of exercising upon compound bodies an influence essentially distinct from what is known as chemical affinity—an influence which consists in the production of a displacement and new arrangement of their elements, without themselves directly participating in it. Assu redly such a power, which is capable of effect ing chemical reactions in inorganic substances as well as in organised bodies, though still too little known to be accurately explained, must play a far more important part throughout na ture than we have hitherto been led to suppose. " In defining it a new power," says Berzelius with philosophic caution, " I am far from wishing to deny that some connexion exists between its influences and the electrochemical ones with which we are familiar. On the con trary, I am very much disposed to recognize it as a peculiar manifestation of these same influences." Another interesting series of facts, which seem to confirm the theory of the operation of chemical affinity in the living body, is that which relates to the evolution of electricity during the ordinary processes of growth both in plants and animals. The late researches of Dr. Faraday have fully proved the identity of electrical attraction with chemical affinity, and have shown that all chemical changes are at tended with a disturbance of electric equili brium. If, therefore, the changes occasioned by the growth of organised systems are imme diately governed by laws similar to those which preside over inorganic matter, we should ex pect to find that electricity is constantly being developed by them in the same manner as we obtain it by chemical decomposition or recom position. There is no deficiency of evidence that such is the case, as the results of late inquiries most abundantly That chemists have not been more successful in imitating the operations of vital chemistry, by the artificial production of organic com pounds, is due not only to their ignorance of the composition of such bodies, but to their want of acquaintance with the film or con dition in which they must he brought together, in order to enter into the desired union. Every
one conversant with chemical operations is well aware of the important influence thus exerted. A slight change of temperature, for example, often reverses the affinities of a body; and many elements are susceptible of particular actions when in a nascent state (i. e. when in the act of being freed from some other combination) which in their ordinary condition could not be so affected. When it is considered, therefore, how little we know of the operation of such conditions in the laboratory of life, no surprise will be felt that its results should often appear contrary to what might have been anticipated. No reasonable ground has yet been adduced for supposing that, if we had the power of bringing together the elements of any organic compound in their requisite states and propor tions, the result would be any other than that which it is found to be in the living body; for the agency of vitality, as Dr. Front justly re marks, " does not change the properties of the elements, but simply combines them in moths which we cannot imitate." It is hoped that the foregoing statements will have established the probability (which is all that the present state of our knowledge on these subjects will allow us to assert) that the affinities which hold together the elements of living bodies, and which govern the elaboration of organic products, are the same as those con stantly operating in the world around. It would seem, at any rate, premature to assert that the operations of vital chemistry are di rected by distinct laws and due to new forces. The designations organic and vital affinity seem to have been employed by some writers to express only the peculiarities of the circum stances and conditions under which these laws usually operate, rather than any real difference in the nature of the powers themselves. And others appear to use them as provisional terms only, referring those effects to the operation of vitality which chemistry is not yet in a condi tion to explain. In the former sense it is ma nifest that such employment of the term is in jurious as leading to misconception. In the latter it is harmless, if it do not check inquiry and create a prejudice against the reception of new facts. The period when all difficulty shall have vanished from the application of chemical laws to the phenomena of the vital economy may be very far distant; and in the mean time " we must be content with gathering a few in diaitions which occasionally break out from the clouds of mystery in which the subject is ob scured." But it must not be left out of view that every fresh discovery adds to the number of these indications, and that they all point in the same direction ; so that the probability of the universal operation of chemical affinity in the living body becomes every day more strong, and the difficulty in proving the existence of a distinct set of vital affinities is constantly be coming less easily surmounted.