principles, albumen, fibrine, and caseine, the molecules of which are still more complex. All that is known on this subject leads to the conclusion that these bodies can only be formed in plants, although they may be transformed one into the other in the animal body. No evidence has yet been produced in favour of the opinion that the animal can form any one sanguigenous compound from food destitute of such compounds. I do not say that this is impossible, but that it is simply an idea conceived, but never yet proved. And the reasons why I believe that it does not happen are two-fold; first, that it is unnecessary, nature providing these compounds in the food of animals; and, secondly, that, so far as we know, very complex atoms can only be constructed out of less complex ones under the influence of a deoxidising process, or at least not by direct oxidation. Now, the process in plants is one of deoxidation, while that of animals is one of powerful oxidation; the result of which is, that the tissues or the food are finally transformed into carbonic acid, water, ammonia, sulphuric acid, and salts, the very compounds which form the food of plants. Indeed, the mutual dependence of plants and animals, the fact that neither overpowers the other, and the still more striking fact, that the atmosphere, by their mutually compensating action on it, is kept uniform in composition, all these considerations prove, that while the chief function of plants is to construct out of simpler molecules the complex atoms of all nutritious matter, the chief result of animal life must be to break up, by oxidation, these complex molecules, and bring them again into a state fit for the food of plants. Now, when we examine the changes in the animal body, we find, just as in the vegetable, a series of compounds intermediate between the tissues and the ultimate oxidised products, which form the food of plants, carbonic acid, water, ammonia, and sulphuric acid. Such bodies are the acids of the bile, one of which is cholalic acid + glycocoll, the other cholalic acid + taurine; cholesterine; the oils and fats, kreatine, kreatinine, inosinic and lactic acids, in the juice of the muscles, and uric acid, urea, allantoine, oxalic acid, &c., in the urine. One point must be alluded to, namely, the formation of fat in the body, since fat is derived from starch, or sugar, by deoxidation, as in plants. But observe, that there is little fat formed, except where respiration and consequently oxidation is defective, or when a large amount of farinaceous food is taken, which of course diminishes the relative amount of oxygen. The way to increase the amount of fat is to give abundance of such food, and to interdict motion. Besides, fat may also be formed by oxidation, if that oxidation acts chiefly on some of the constituents, thus splitting up a complex molecule perhaps into two parts, one of which takes up all the oxygen, the other becomes fat by losing oxygen. Indeed it is probable that when fat is formed from sugar, it is because a part of the oxygen required for the oxidation of the tissues is taken from the sugar, when respiration does not supply the whole. The fat itself, when formed, is oxidised like the other compounds. After this sketch of the general nature of the processes in plants and animals, you are prepared to understand that we are now able in some degree to imitate both. It is here that organic chemistry has of late done most, and will yet do much more. But, as might be expected, we find it much easier to destroy, by various means, the complex molecules of organic nature, than to build up such molecules from simpler ones. The most powerful agent we have is oxidation, and by its means we can produce, from complex organic bodies, a large number of less complex products found in nature. We possess, also, the various processes of fermentation, putrefaction, and decay, by which we can produce similar results. Thus by oxidising uric acid, we can form urea, allantoine, oxalic acid, ammonia, carbonic acid, and water, all of which are formed from it in the body. By oxidising the albuminous or sanguigenous bodies, we can form such products as formic, acetic, propylic, butyric, valerianic, and benzoic acids, besides various crystalline products, such as glycocoll, leucine, and tyrosine,the two former found in the body, the latter not yet found in nature, as well as oil of bitter almonds, hydrocyanic acid, ammonia, and of course CO, and HO. 2 By oxidising oils, we can produce many of the volatile oily acids. By oxidising sugar or starch, we can produce oxalic and formic acids. By the fermentation of sugar, we can produce (see Example 15) first, alcohol and carbonic acid; second, lactic acid; third, gum and mannite; fourth, butyric acid; fifth, amylic, alcohol, and capric acid. By the fermentation of amygdaline, we can produce oil of bitter almonds, hydrocyanic acid, sugar, and formic acid. The oil of bitter almonds, by oxidation, becomes benzoic acid. Hippuric acid (see Example 16), boiled with hydrochloric acid, yields glycocoll and benzoic acid. By the oxidation of salicine, we form salicylic acid and also the oil of spirea. Wood, when distilled, yields, among other products, pyroxylic spirit, or hydrated oxide of methyle; and we find in the oil of Gaultheria procumbens, salicylic acid combined with oxide of methyle. By the fermentation of salicine, we form grape sugar and saligenine. By that of asparagine, we obtain succinic acid, which is also formed in the fermentation of malate of lime. In all these cases, and many more, complex molecules are resolved into less complex, as we approach nearer to CO, HO and NHg. EXAMPLE 15. Lactic and Butyric Fermentations. Lactic Acid. Sugar of Milk. 12 8 8 Carbonic Acid. Hydrogen. + 4 CO2 + H2 EXAMPLE 16. Decomposition of Hippuric Acid. Hippuric Acid. C18 H, NO + 2 HO C11 Ho O4 + C1 H ̧ NO. 5 But although the task is more difficult, we have also made some progress in the opposite process, that of building up more complex out of less complex molecules. It is true, we have succeeded, as yet, in very few instances in thus producing natural products. Artificial urea (see Example 17), however, is a proof that it is not impossible. A solution of cyanate of ammonia passes rapidly into urea when warmed. A solution of cyanogen yields 10 or 11 products, several of which are much more complex than cyanogen, as urea, oxalate of ammonia, &c., and a black body, certainly more complex than cyanogen. Malate of ammonia yields aspartic acid, &c. But we have succeeded in producing a large number of compounds, which, if not identical with natural compounds, are perfectly analogous to them. Thus we have formed a large number of bases, both volatile and fixed, which approach closely in composition, and also in properties, to natural bases. The bases in the large table (No. 11) so far as known, are examples of this. Here we add, to the molecule of amide, a still more complex molecule, C, H, C4 H5 or C10 H11, replacing H in NH, and we thus obtain bases closely analogous to ammonia. Aniline, already mentioned, is a similar base of another series. In it, amide is combined with C12 H,, replacing H in NH, and this series of bases is closely analogous to the natural volatile bases, coniine and nicotine. Again (see Example 18), we can replace two or all three of the eqs. of H in NH, either by 2 or 3 eqs. of ethyle, methyle, amyle, or phenyle, &c., or by 1 or 2 of one of these, and 2 or 1 of another. Nay, further (see Example 8), we can replace 1 and sometimes 2 eqs. of H, in aniline for example, by NO,, which then, strange to tell, plays the part of H, and the result in this case is nitraniline, a beautiful crystalline base, and the type of a series containing the same elements as the natural fixed bases, morphine, quinine, strychnine, and the like. One very striking example of the power we have of building up more complex out of less complex molecules is afforded by the oil of bitter almonds. When this oil is acted on by ammonia (see Example 19), there is formed from 3 eqs. of the oil and 2 of NH,, 6 of HO being separated, the body C12 N, H1g. Here is a complex molecule. The body, hydrobenzamide, is neutral; but when boiled with potash, 2 eqs. coalesce to form one of a base, amarine C, N, Hse, which much resembles natural bases. By the same 42 4 2 18. process, from oil of bran or furfurole (see Example 20) is produced by NH,, first, furfuramide, a neutral body; and when this is boiled with potash, 2 eqs. coalesce to form one of a new base, furfurine, which not only resembles the natural bases, but is actually used as an antiperiodic remedy. It is to be noted that almost all the processes by which we produce more complex from less complex molecules are processes of reduction. The action of ammonia tends to remove oxygen in the form of water; and a whole class of bases are obtained by the action of a very powerful reducing agent, hydrosulphuret of ammonia, on substitution products in which H has been replaced by NO,. It can hardly be doubted that, in process of time, we shall discover the means of producing the natural bases, such as morphine and quinine. We already know how we could with certainty produce coniine and nicotine if we had only the corresponding carbonhydrogens, bearing the same relation to these bases as benzole or hyduret of phenyle does to aniline (see Example 21). And these oils or carbohydrogens will very probably soon be discovered. In the same way, if we can discover, as we probably shall, the true constitution of morphine and quinine, and the substance from which the plants form them,-which will one day be done by studying the juices of these plants in all stages of growth, we shall then have little difficulty in forming such bases. We have the principle and the process, the materials only are wanting. EXAMPLE 18. Bases derived from the Ethyle Series, &o. EXAMPLE 21. Analogy between Aniline, Coniine, and Nicotine. 12 2 Aniline, C, H, N, is derived from Benzole, C12 H。. 5 0 15 10 5 It is tolerably certain, that the materials out of which plants form the albuminous bodies are sugar and ammonia, or some compound of ammonia along with sulphuric acid, and that the building up process is one of reduction, chemically speaking. But here another principle comes into action, namely, the vital principle, that which gives to the tissues an organised structure. And this is beyond our reach. I do not regard it as impossible, or even very improbable, that we may one day succeed in producing a compound with the chemical composition and chemical characters of albumen, fibrine, caseine, or gelatine. But the formation of a cell, the foundation of all organised structure, is not entirely a chemical, but partly a vital process, and therefore I do not anticipate the possibility of our ever producing fibres, membranes, blood globules, or even the imperfect structure observed in white of egg. But, notwithstanding, nothing can be more certain than this, that every change in a plant or animal is, apart from structure, a purely chemical change, and that these changes cannot possibly be understood without the aid of chemistry. Hence chemistry is absolutely indispensable to a knowledge of the laws, both of health and disease, to physiology and to pathology. When we consider that the plant from CO2, HO, NH,, SO, and salts, produces the whole ascending series of vegetable products, ending in the albuminous bodies, and that in animals we have, as the result of oxidation, a descending series, ending in CO2, HO, NH,, SO,, and salts, it is impossible to doubt that chemical action is a chief agent in vegetable and animal life. All these changes are chemical, and cannot be otherwise. They are influenced, indeed, essentially, by the vital force, but still they depend also on chemical laws, the very same laws as act in the mineral world, but here combined with, and subordinate to, the vital organising force. Time will not permit me to dwell at length on the recent progress and present state of physiological and pathological chemistry. In truth, the genuine application of chemistry to physiology and pathology is yet in its infancy. We are hardly yet acquainted with the chemical nature of the best known fluids and solids of the body. In proof of this, I may refer to the urine. It is only of late years that we know that the acid re-action of healthy urine is due to the property possessed by phosphate of soda of dissolving free uric and hippuric acids. The extractive and colouring matters of the urine are hardly investigated; yet we already know that they contain a substance closely allied to, if not identical, as I believe it is, with one of the products of destructive distillation, or imperfect oxidation, namely, carbolic acid, a body nearly allied to creosote, and having many of its properties. Again, the presence of hippuric acid, of kreatine and of kreatinine in urine, is quite a recent discovery, due to Pettenkofer, Heintz, and Liebig. Further, it has been recently shown, that the compounds which give to the solid excreta their peculiar odour, are produced by the imperfect oxidation of albuminous matters, and may be formed artificially, but have not yet been studied. Thus we see that products of imperfect oxidation, such as uric acid, urea, oxalic acid, kreatine, kreatinine, hippuric acid, and the bodies just mentioned, as found in the extract of urine, and in the solid excreta, are removed from the body by the kidneys and intestines; while others, such as oily acids, escape through the skin on the sweat. But our knowledge of all these excreta is still imperfect. Then the fluid which pervades the muscles, and which contains, besides other bodies, albumen, kreatine, kreatinine, inosinic acid, a large amount of lactic acid, and acid phosphate of potash, has only been recently studied at all. The gastric juice is analogous to that fluid. In the blood, urea, cholesterine, fat, bile, and even uric acid, have lately been detected, as was to be expected, although the detection is very difficult, from the very small relative proportion of these matters. Perhaps bile is only found in the blood when its amount is morbidly increased, but cholesterine is more easily detected. The chemistry of the pancreatic juice, since Bernard's experiments on its power of dissolving or suspending fat, has become a grand desideratum. That of the brain and nerves may be regarded as hardly begun, and is of surpassing interest. During the past year, it has been shown by Liebig, that the fibrine of blood is a different body from that of the muscles—at least, that it has different properties. Here is another vast field for research, even in the healthy body. In the bile (see Example 22), after many laborious and excellent researches, the last investigation, that of Strecker, has really simplified the matter to a great degree, although there is much to do even there. It is now known that the bile is a salt or soap of soda-not, as was supposed of one acid, the choleic acid, combined with soda, but a mixture of two such salts, the acids in which differ. One of NEW SERIES.-NO. XVIII. JUNE 1851. 4 F these, choleic acid, consists of a non-nitrogenous acid, now called cholalic acid, coupled with glycocoll, the same weak base which is obtained by the action of acids on gelatine and on hippuric acid. The other acid of the bile, choleic acid, is composed of the same cholalic acid, coupled with taurine, a crystalline substance containing a large amount of sulphur. Hence one of the acids of bile contains sulphur, the other not. Strecker has also shown that the bile of the pig contains a peculiar acid, hyocholic acid, differing slightly in composition from the acids in the bile of other animals. We see, therefore, that we are only beginning to become well acquainted with the animal fluids and solids. But we are on the right path, and our progress will daily become more rapid, if we adhere to the inductive method, and do not allow ourselves to be blinded by theory. EXAMPLE 22. Composition of the Acids of the Bile. Cholic Acid, C52 H43 NO12 yields Choleic Acid, C52 H45 NS2 O14 yields 010 010 2 The sum, C, H, NS2 06, is Let me here allude to the remarkable fact (see Example 23), that the alkaline re-action of the blood is due to the phosphate or carbonate of soda, and is essential to its fluidity, while the acid re-action of the juice of muscle depends on the presence of acid phosphate of potash. Free phosphoric acid is essential to the formation of tissues. It is present along with oil in the yolk of egg. Looking at the salts in blood, and in the juice of flesh, in another view, both of these salts are tribasic; but the former contains 2 eqs. of soda and 1 of basic water, the latter 1 eq. of potash and 2 of basic water, according to the observations of Graham. The latter has an acid, the former an alkaline, re-action; yet the blood and the juice of muscle are only separated by very thin membranes. They do not mix; for kreatine and lactic acid, which occur in the latter, are not found in the blood. Now, an acid and an alkaline liquid, in contact with moist solids, furnish some of the essential conditions of electric currents. And now we know, that electric currents, as has been shown by Matteucci and Dubois Reymond in different ways, do occur in the body. The wonderful arrangement I have alluded to, by means of the two phosphates, is probably somehow concerned in these currents. Observe, I by no means identify the vital force with electricity. On the contrary, I hold that electricity is only one of the results of chemical action going on under the influence of the vital force, whatever that may be. Here is another fertile field for research, and one of the highest interest. EXAMPLE 23. Soluble Phosphates of Blood and Flesh. Phosphate of Soda in blood, PO5, 2 Na O, HO, has an alkaline re-action. On the whole, it appears that while organic chemistry, as an instrument of research, has made, and is making, very rapid progress, we are hardly yet doing more than beginning to use that instrument for the due investigation of physiology and pathology. But as we have every reason to think that we have found the true path, the prospect before us is extremely encouraging. There is no department of these subjects yet fully understood. Even the process of respiration has been of late repeatedly investigated, and with most valuable results. It has been shown, for example, that an animal, which would soon die in an atmosphere containing a small per centage of carbonic acid more than the air does, as is the case in expired air, can live without inconvenience in an atmosphere containing 17 or 18 per cent. of carbonic acid, provided the amount of oxygen be also increased. This is explained by the fact, that venous blood, or F |
