CHEMICAL FINAL CAUSES, AS ILLUSTRATED BY THE PRESENCE OF PHOSPHORUS, SENTIENT ORGANISMS. THE HE recent unexampled progress of Anatomy, Chemistry, and Physiology, has brought into startling prominence a problem which may be thus stated, "Why do certain Chemical elements or ingredients, rather than others, enter into the composition of Plants and Animals ?" This question has probably been put to himself more or less clearly, by every considerate student of the Sciences named above, and has unconsciously guided researches which did not professedly deal with it. There is not one, moreover, of our great Physiologists and Chemists who has not long meditated on this problem, and largely contributed to its solution, but their replies in the majority of cases, have been indirect and implicit; sometimes indeed instinctive rather than intentional; and those whom they have addressed have often failed to perceive that a question had been proposed, and an answer to it given. A very few have distinctly considered the problem, among whom a foremost place must be assigned to the learned Lehmann1 in whose writings such phrases as "the physiological value" of an element continually occur, and who is induced only by a sense of the complexity of the 1 Physiological Chemistry by Prof. G. C. Lehmann, vol. i. Translated for the Cavendish Society by Prof. G. E. Day, St. Andrews. Methodological Introduction, pp. 10, 25. inquiry, and the hopelessness in the present state of our knowledge of disposing of its difficulties, to adjourn its discussion for a season.1 As for the great majority, again, of educated, intelligent, medical men and others conversant with Chemistry and Physiology, if such queries are addressed to them as, "Why do our skeletons consist of bone, rather than of wood, or flint, or marble? Why are our teeth composed of ivory rather than of steel? Why is our blood charged with iron, rather than with gold?" they are simply startled and make no reply. And truly no reply but a most imperfect one, is or ever will be possible; nor is it otherwise than with the utmost diffidence, that I attempt to suggest why only certain of the elements occur in living organisms. The question however is certainly one worth attempting to answer, because its consideration cannot but lead us to ennobling meditations of God, one of whose glories it is "to conceal a thing;" whilst to the extent that we can answer it we shall enlarge the domain alike of the Science of Biology and of the Art of Medicine. For no one will doubt that Science would gain by the disposal of the problem before us; and it is scarcely less evident that if we knew one reason, still more each of the reasons, why even one element, not to say all the organismal elements are present in our bodies, we should be better able by the amount of that knowledge to preserve health and to cure disease. The problem thus awaiting a fruitful solution is as follows. Our globe, including the atmosphere, and the ocean with its tributary waters, consists in very unequal proportion of some sixty substances, which according to our present knowledge are simple or elementary. Of these sixty chemical elements, less than a third are found distributed throughout the entire Vegetable and Animal Kingdoms. Of this fractional third, one half occur only in small quantity, so that the greater part of the bulk and weight of plants and animals is made up of one fifth or one sixth of the whole elements; and the greatest part consists of but three, Carbon, Hydrogen, and Oxygen. This will appear from the accompanying table, in which the chemical elements occurring in The Organismal Elements. 303 plants and animals are distinguished from those known to be absent from their tissues, or not yet recognised as present. The ever-present elements of Plants and Animals, I have distinguished as Organismal rather than as Organic; because on the one hand, the whole of the elements found in living structures, are also found in Inorganic masses; and on the other hand, many organic substances (according to the Chemist's definition of such), as Kakodyle, Stibio-methyle, and Zinc-ethyle, contain respectively Arsenic, Antimony, and Zinc, which are not normal constituents of plants or animals, and unless in the smallest quantities are deadly to all of them. The elements marked with a (?) are those which have either been occasionally detected in plants and animals, or which there are reasons for thinking would be found if sought for. Claims were at one time largely set up for arsenic, and lead, as present in all animals in small quantities, but those claims are now generally disallowed. A similar claim, but on better grounds, has been urged in behalf of copper, which is sometimes present in the human body, and is apparently never absent from some of the Mollusca, Cephalopoda, Ascidia, and Crustacea.1 1 See in reference to the three metals in question, Lehmann's Phys. Chem. vol. i. pp. 449, 450. The Possible Organismal Elements. 305 Of the two missing non-metallic elements, Selenium, the analogue of sulphur, may be found accompanying the latter in the sulphur-compounds of the animal organism; and Boron, the salts of whose oxy-acids resemble those of carbon and silicon, may be associated with the alkaline carbonates and phosphates. Neither of these elements has as yet been sought for. It may seem at first sight, questioning the sufficiency of the Chemist's "victorious analysis" to detect every ingredient of a complex whole, to hint that he may have missed certain organismal elements because he did not seek for them; seeing that he professes his ability to resolve an unknown composite substance into each of its ingredients, however numerous they may be, provided only they are all among the recognised sixty (or more) elements. But in reality, the Physiological Chemist has never done more than say, "this is present," and has always left a margin for those possible elements which had not been objects of search with him. No deliberate, exhaustive inquiry into all the elements of any plant or animal has ever been instituted, and till it shall be, a query may be put in every list of organismal elements over against all the so-called chemical simple substances; although it is manifest that, in the case of the human organism, we know all the elements which are present in large quantity in it. At the same time, when we find an organic compound so easily detected as sugar, overlooked, till very recently, in the secretions of the liver; and so familiar a substance as ammonia, after being positively pronounced, by the most skilful and impartial Chemists, to be totally absent from the blood, demonstrated, to the satisfaction of the most competent judges, to be one of its never failing and most important constituents, we must avoid dogmatising on what substances may yet prove to be essential ingredients, even of those organisms which have for the longest time been objects of study. And as quantity is no measure of value in the case of an organismal element, we must apply a similar rule to the rarest simple substances. More than five years of research have enabled me to demonstrate the universal distribution of Fluorine throughout the mineral, vegetable, and animal kingdoms, and especially its occurrence in the higher organisms; X |