The Fitness of the Environment

After what has gone before it will not be necessary further to discuss the second great qualification of an environment — stability of conditions in the ocean. The principal physical conditions and chemical compounds therein are constant; that is the whole case. But it is a case which cannot be bettered. Certainly nowhere else where life is possible, probably in no other place in the universe except another ocean, are so many conditions so stable and so enduring.

The regulatory devices of our modern labo- ratories have not yet succeeded in rivaling the ocean. Singly, certain conditions, for example, temperature, alkalinity, and concen- tration, may be more accurately regulated by " man, though on a small scale only ; but the regulation of all such properties together is not yet possible. The only known improve- ment upon the ocean is the body of a higher warm-blooded animal. Here, however, the processes of organic evolution have begun with the ocean, and in several respects merely perfected existing arrangements.

This statement is far from fanciful. Not only do the body fluids of the lower forms of marine life correspond exactly with sea water in their composition, but there are at least strong indications that the fluids of the highest animals are really descended from sea water, from the sea water of an earlier epoch, to be sure, and they are not changed beyond recog- nition by the transformations of evolution.^ A comparison of the relative amounts of various saline constituents in sea water and in mammalian blood (roughly averaged from a variety of measurements in different species) will demonstrate this relationship.

' See the interesting paper by Macallum, Transactions of the Royal Society of Canada, 1908, 11, p. 145. The gaps in the table do not indicate that substances are lacking, but merely that the amounts are small. In short, the same sub- stances are present in both cases, and in both cases sodium chloride largely predominates. The importance of carbonic acid in metabo- lism accounts for the large amount of sodium bicarbonate in the blood, and this raises the amounts of both sodium and carbonic acid.

It is also to be noted that the regulatory processes in the ocean and in the organism are in one or two aspects similar, e.g. tempera- ture regulation by evaporation, and regula- tion of the alkalinity. Of course no impor- tance attaches to such resemblances, beyond the fact that both regulations are highly favorable, because of the special fitness of water in one case and of carbonic acid in the other. But it is at least worthy of mention that the regulation of the ocean in general bears a striking resemblance to a physiolog- < ical regulatory process, although such physi- ological processes are supposed to be the result of organic evolution alone. Very much this same idea occurred to Palitzsch in the course of his investigation of the alkalinity of the ocean.^ The resemblance is more ob- vious still when the stability of all the more

important physical conditions of the ocean is taken into account. Indeed, however difficult it may be to make out those subtle traits of physiological processes which account for their efficiency, their adaptability, and their exactness, I feel sure that no one who is thoP oughly conversant with the general char- acteristics of the life process can fail to see a rough counterpart in the means by which conditions in the ocean are regulated. ^ It is certainly a salient, and hardly a mean- ingless fact that the processes of inorganic and organic evolution have a similar out- come in complex, exact, and almost ideally efficient activities. Is it not possible that in the case of the organic processes some have now and then been regarded as adaptations which in reality arose automatically and quite inevitably ?

The existence of efficient regulation of the ocean, establishing its most important physico- chemical characteristics as constants, is of far greater importance in the sciences of nature, especially for living organisms, than could formerly have been guessed. Such natural processes were perhaps even necessary to make life possible in the birthplace of life. I cannot undertake to explain the very great importance which to-day the physical chemist attaches to the regulation of the conditions of a chemical process. The only way to gain an idea of this is to examine a work on physi- cal chemistry. Certainly, however, nothing has lately arisen more essential to biology than the understanding of the influence of temperature, pressure, reaction, concentration, ionization, etc., upon all physico-chemical structures and changes, whether inorganic or vital.

Thus the fitness of the ocean appears as an embodiment of the physical fitnesses of water and carbonic acid, resulting directly and in- evitably from these and other natural phenom- ena, and providing a lodgment for life and a medium for its earlier development upon the earth. No philosopher's or poet's fancy, no myth of a primitive people has ever exag- gerated the importance, the usefulness, and above all the marvelous beneficence of the ocean for the community of living things.

A HUNDRED years ago the firm belief was held by all chemists that whatever substance is synthesized within the body of the living organism possesses special and pe- culiar characteristics of its own, which mark it oflf from all inorganic bodies, and divide chemistry into the two great and perfectly distinct departments of Organic Chemistry and Inorganic Chemistry. To be sure, even then many organic substances had been sep- arated from the organism, purified, and sub- jected to the usual experiments of the labora- tory, without at any stage manifesting unique properties. But, as Berzelius believed, a special vital force had presided over their formation, and this, therefore, he supposed to be impossible under any other circum- stances.

In the course of time, however, a long series of successful syntheses of undoubted constitu- ents of animals and plants, among which Woh- ler's preparation of urea in 1828 is the most famous, completely destroyed the old erro- neous assumption. The compounds of organic chemistry gradually came to be recognized as different from inorganic substances only in the sp ecial characteristic s of the element s c arbon, hydrog enj_aiid_oxygen when in chem- ical union with one another, ]ust as the com- pounds of any other elements have their own specific characteristics. No other difference remains; every principle of chemical science applies to organic and inorganic substances alike; and accordingly life has been for- ever subjected to the general laws of chem- istry.

As syntheses multiplied, the organic chem- ist found many fields for investigation where life was not concerned. The application of- his new substances in the arts, as well as many fascinating theoretical problems, led him on, until, about the middle of the century or a little later, it became clear that organic sub- stances in the original sense are but a small part of his scope. His occupation had be- come the study of all the compounds of carbon, wherever and however they might

occur, and as a rule he had little to do with physiological or biological chemistry. Not that he was now ever disposed to distinguish between substances which happened to occur in living organisms and others ; for at length he had completely accepted the view that, apart possibly from a few complicated sub- stances like the proteins, such distinctions are thoroughly irrational. But the nature of the subject and the historical accidents of its development directed his attention in the main elsewhere.

Nevertheless, the distinction between or- ganic chemistry as the science of all the com- pounds of carbon, and inorganic chemistry as the science of all other chemical compounds whatever has persisted, and not without sound reasons. In the course of the wonder- ful development of organic chemistry, which must ever be counted as one of the greatest achievements of the nineteenth century, enor- mous numbers of new chemical substances were discovered. In 1883 the number of carbon compounds had reached 20,000, in 1899, 74,000, and in 1902 it exceeded 100,000.^

> See M. M. Richter, "Lexikon der Kohlenstoffverbindun- gen," Hamburg and Leipzig, 1900, continued in supplemen- tary volumes. This work catalogues all the compounds of carbon as they come to light. This is the sufficient practical ground for pre- serving organic chemistry as a separate sci- ence. The subject is so vast that in fact it is impossible to incorporate it with other departments of chemistry. Even the com- pounds of carbon and hydrogen alone are counted by hundreds, those of carbon, hydro- gen, and oxygen, by thousands, and the number of possible compounds of the three elements is almost unlimited.

The mere number of organic compounds is, however, far from constituting the only dis- tinction between the two departments of descriptive chemistry. The unique variety of compounds containing carbon, hydrogen, and oxygen, and, in a small proportion of cases a few other elements besides, must obviously rest upon the nature of the elements them- selves, especially of course upon the nature of carbon, upon the properties which are pe- culiar to them and which mark them off from' other elements, just as the properties of argon, of the metals of the alkalies, or of the halogens determine their own chemical be- havior. Moreover, such characteristics must and do contribute properties to the com- pounds of carbon which are theirs as a class, which distinguish them from the compounds of other elements in somewhat the same way

that the anatomical characteristics of one class of animals distinguish such a class from other classes of animals. In short, the carbon compounds are not unique merely because they are numerous; they are uniquely nu- merous because they are compounds of carbon with hydrogen, oxygen, and in some cases certain other elements. They possess, more- over, other less obvious class properties as well, though of these, it must be admitted, chemistry is even yet far from a clear under- standing. But unquestionably that is due to the incompleteness of the science, for the peculiar methods of organic chemistry are a sufficient guarantee of the existence of such class peculiarities.^

In our present investigation a study of the possibilities of chemical union between the elements carbon, hydrogen, and oxygen is of great importance, and accordingly we must now examine some of the results of synthetic organic chemistry. * See the introductory chapter to Meyer and Jacobson's "Lehrbuch der Organischen Chemie," Leipzig, 1907. The principal theoretical foundation of organic chemistry is the idea of valence. Let us consider the chemical formulas of a number of the simple compounds of hydrogen, e.g. HCl, H2O, NH3, CH4, HI, HBr. It is evident that in such formulas a single atom of hydrogen is never represented as in union with more than one atom of another element. There are, however, cases where one atom of hydrogen is in union with a single other atom, e.g. HCl, HBr, HI; or two atoms of hydro- gen may unite with a single other atom, e.g. H2O; or three atoms of hydrogen with one other, e.g. NH3; or four hydrogens with one other, e.g. CH4. If the assumption be made that discrete bonds or forces take part in the union of atoms, hydrogen must possess but a single such bond or valence. Otherwise com- pounds of the type X-H-X, X-H/J, or

of some other type in which one atom of hydrogen is in union with more than one atom of lower valence, must exist, and this is con- trary to fact. We may, therefore, employing a dash to represent valence, write the constitutional formulas of hydrochloric acid, water, and methane, as follows : — Accordingly, oxygen appears to possess two valences and carbon four. These conclu- sions are justified by an almost inconceivable wealth of experience; they are the means of constructing the elaborate constitutional for- mulas which are so necessary a part of organic chemistry; and there can be no doubt that in almost all the compounds with which we shall be concerned hydrogen is invariably univalent, oxygen bivalent, and carbon quad- rivalent. On this basis the construction of possible formulas of organic compounds is merely an exercise in a somewhat peculiar department of mathematics.

The compounds of carbon and hydrogen may first be considered. With but a single atom of carbon in the molecule one only is representing the compound ethane is ob- tained ; but if the process be extended, great complexity speedily ensues. For example, the hexanes, compounds formed upon this plan containing six carbon atoms, all of one empirical formula, number five. Their con- stitutions are represented by the accompany- ing structures, every one of which corre- sponds to a known substance : —

In each of the compounds represented by these formulas every carbon atom is believed to have four valences and every hydrogen atom one. \ As the number of carbon atoms in the mole- cule increases the number of possible forms, isomers so called, multiplies with great rapid- ity. Of compounds C7H16 there are 9 forms; for CgHis, 18; for C9H20, 35; for C10H22, 75; for CiiH24, 159; for C12H26, 355; for C13H28, 802; and for C14H30, 1855 possibilities.^ There can be no reasonable doubt that the prepara- tion of each and all of these compounds would be possible, and that once formed they would be very stable substances. In truth, no one

has ever failed who has set out with skill, a good plan, and suitable starting materials, to prepare such a body. The number and variety of hydrocar- bons is further enormously extended by the possibility of ^dQ]il)le and treble unions be- tween pairs of fearbon atoms, as in effiyTene, Further, more than one double or treble bond, or single, double, and treble bonds in combination, may occur, as in the well-known substances CH3 - CH = CH2, CH3 - C = CH, CH2=C = CH2, etc.

Finally, the carbon atoms possess the prop- erty of uniting to form ring compounds in great variety, e.g. Moreover, such rings may unite with carbon chains, both those containing single bonds, and those containing double and treble bonds, whether straight or forked, in great variety; and also with other rings, e.g. It is quite impossible briefly to indicate, still less to give an adequate idea of the bewildering diversity and complexity of the known hydrocarbons. They exist by the hundreds, and there are certainly countless thousands of possible stable bodies made up of carbon and hydrogen alone.

With the addition of oxygen, the variety and number of known and of possible substances is still further multiplied. Oxygen may enter , into the following types of union with carbon and hydrogen in organic compounds : — Alone or in combination, these groups yield a great variety of important classes of com- pounds. Representing a group or radical consisting of carbon and hydrogen alone by R, a few of the most simple and important divisions are as follows : —

By the introduction of oxygen into the molecule any complex hydrocarbon may be converted into a great number of substances, and even in simple cases such derivatives are not few. In the accompanying formulas I have gathered together the possible hydro- carbons, containing three carbon atoms (ex- cluding ring compounds), and their possible oxygen derivatives, most of which are capa- ble of existence as substances of varying stability, many of them being in fact well- known common substances like lactic acid, glycerine, propionic acid, propyl alcohol, two of the simplest sugars, etc.

This is relatively a simple case. As the number of carbon atoms in the molecule increases, the number of possible oxygen derivatives multiplies in a far more rapid progression than in the case of the simplest hydrocarbons, which has been stated above. Accordingly there can be no doubt that in addition to the many thousands now known, the existence of countless millions of com- pounds consisting of carbon, hydrogen, and oxygen alone is possible. In a large propor- tion of cases the only difficulties involved in their preparation are to obtain suitable start- ing materials, and the enormous labor of the process. There are, for instance, hundreds of thousands of possible hydroxyl derivatives alone of the paraflfine hydrocarbons of the formula C14H30, but only one of these is now known.^ Yet all, or at least a vast majority, would unquestionably be stable bodies if once formed.

Not less important than the number and variety of such substances is their ^iverSty; of physical and chemical characteristics. The following are, for example, individiial chemi- cal compounds of at least moderate purity, made up of the three elements alone : al- cohol, formaldehyde, acetic acid, carbolic acid, oxalic acid, acetone, ether, lactic acid, sugar, cotton, glycerine, olive oil, camphor, tannin, ophiotoxin (the chief poisonous con- stituent of cobra venom), starch, vanilline (the flavoring constituent of the vanilla bean), oil of wintergreen, salol, benzoic acid, digita- line.

Here is a variety that baffles description; but description is hardly necessary, for the facts explain themselves. In short, the com- pounds of the three elements which compose water and carbon dioxide exist in enormous numbers and in unparalleled diversity of chem- ical and physical characteristics. They in- clude substances of the greatest stability, and others of exceeding instability ; liquids, solids, and gases ; chemically active and chemically inert bodies; acids and neutral substances; substances' which are readily oxidized and others which are oxidized only with great difficulty. In a very large proportion of cases these compounds are capable of enter- ing into reactions with one another. They are, moreover, capable of forming still more complex substances, in still greater variety by entering into union with other elements, notably with nitrogen and sulphur.

The organic substances which contain nitrogen are very numerous and exceedingly diverse in their properties. A few of the principal classes of such compounds are the following : — Derivatives of purine, pyridine, and other ring systems, etc. The nitrogenous organic substances include classes of compounds which differ in their properties from any of the non-nitrogenous substances. Of such special properties the most conspicuous is perhaps alkalinity. Like ammonia, of which it is a derivative, the amino group (— NHg), and various other groups containing nitrogen possess this char-

acteristic. Such compounds, accordingly, supplement those which contain the acid carboxyl group ( — COOH) and make possible the fundamental relations of acid, base, and salt among organic compounds, corresponding to those of inorganic chemistry. There exist also many compounds of sul- phur, of chlorine, bromine, and iodine, as well as of various less common elements among organic substances ; but in all such cases the complexity and variety of the compounds depend primarily upon the ca- pacity of carbon, hydrogen, and oxygen, or carbon and hydrogen together, to form nu- merous, varied, and complex compounds on which, as it were, the further complexity is superposed.

Thus the great diversity of organic sub- stances depends in the first instance upon the quadrivalence of carbon, which makes of tfe' carbon atom in the organic molecule a focus, from which chains of atoms may ex- tend in four different directions; or, in the case of double or treble ties, in three directions ; ■<-Cs>. Next comes the fact that carbon atoms, when otherwise exclusively in com- bination with hydrogen, and under other circumstances in lesser degree, possess an almost ualiiriited__.cap.aciJtyLjto_joinJj3^ether and form chains^ and rings in great variety. The longest carbon chain yet synthesized oc- curs in the compound hexakontane,^ C60H122, a substance whose constitution is probably as follows : —