COMPARISON OF ORGANISMS.

23

of the analysis of the human organism to establish the resemblance he exhibited between the skull and the other elements of the vertebral column.

Of phases of the same organism.

one aspect,

A new order of resources presents itself when we compare the different phases of the same organism. Its chief value is in its offering, on a small scale, and, as it were, under the whole series of the most marked organisms of the biological hierarchy; for it is obvious that the primitive state of the highest organism must present the essential characters of the complete state of the lowest; and thus successively, without, however, compelling us to find the counterpart of every inferior term in the superior organism. Such an analysis of ages unquestionably offers the property of realizing in an individual, that successive complication of organs and functions which characterizes the biological hierarchy, and which, in this homogeneous and compact form, constitutes a special and singular order of luminous comparisons. Useful through all degrees of the scale, it is evidently most so in the case of the highest type, the adult Man, as the interval from the origin to the utmost complexity is in that case the greatest. It is valuable chiefly in the visible ascendant period of life; for we know very little of the fœtal period; and the declining stage, which is in fact only a gradual death, presents little scientific interest: for, if there are many ways of living, there is only one natural way of dying. The rational analysis of death, however, has its own importance, constituting a sort of general corollary, convenient for the verification of the whole body of biological laws.

Of different organisms.

The popular notion of comparative biology is that it consists wholly of the last of the methods I have pointed out: and this shows how pre-eminent it is over the others; the popular exaggeration however being mischievous by concealing the origin of the art. The peculiarity of this largest application consists in its being founded on a very protracted comparison of a very extensive series of analogous cases, in which the modification proceeds by almost insensible graduated declension.

The two more restricted methods could not offer a series of cases extensive enough to establish, without con

firmation, the nature and value of the comparative method, though, that point once fixed, they may then come into unquestionable use. As for the value of the largest application, it demonstrates itself. There is clearly no structure or function whose analysis may not be perfected by an examination of what all organisms offer in common with regard to that structure and function, and by the simplification effected by the stripping away of all accessory characteristics, till the quality sought is found alone, from whence the process of reconstruction can begin. It may even be fairly said that no anatomical arrangement, and no physiological phenomenon, can be really understood till the abstract notion of its principal element is thus reached, by successively attaching to it all secondary ideas, in the rational order prescribed by their greater or less persistence in the organic series. Such a method seems to me to offer, in biology, a philosophical character very like mathematical analysis genuinely applied; when it presents, as we have seen, in every indefinite series of analogous cases, the essential part which is common to all, and which was before hidden under the secondary specialities of each separate case. It cannot be doubted that the comparative art of biologists will produce an equivalent result, up to a certain point; and especially, by the rational consideration of the organic hierarchy.

This great consideration was at first established only in regard to anatomy; but it is yet more necessary in physiology, and not less applicable, except from the difficulty of that kind of observation. In regard to physiological problems particularly, it should be remarked that not only all animal organisms, but the vegetable also, should be included in the comparison. Many important phenomena, and among others those of organic life, properly so called, cannot be analysed without an inclusion of the vegetable form of them. There we see them in their simplest and most marked condition, for it is by the great act of vegetable assimilation that brute matter passes really into the organized state, all ulterior transformations by means of the animal organization being much less marked. And thus, the laws of nutrition, which are of the highest importance, are best disclosed by the vegetable organism.

IMPERFECTION OF THE COMPARATIVE METHOD. 25

The method is unquestionably applicable to all organs and all acts, without any exception; but its scientific value diminishes as it is applied to the higher apparatus and functions of the superior organisms, because these are restricted in proportion to their complexity and superiority. This is eminently the case with the highest intellectual and moral functions which below Man disappear almost entirely; or, at least, almost cease to be recognizable below the first classes of the mammifers. We cannot but feel it to be an imperfection in the comparative method that it serves us least where we are most in need of all our resources; but it would be unphilosophical to deprive ourselves, even in this case, of the light which is cast upon the analysis of Man as moral, by the study of the intellectual and affective qualities of the superior animals, and of all others which present such attributes, however imperfect our management of the comparison may yet be. And we may observe that the comparative method finds a partial equivalent in the rational analysis of ages, thus rendered more clear, extensive, and complete,-for the disadvantages which belong to the same stage of the biological hierarchy.

Thus I have presented the principal philosophical characters of the comparative method. It being the aim of biological study to ascertain the general laws of organic existence, it is plain that no course of inquiry could be more favourable than that which exhibits organic cases as radically analogous, and deducible from each other.

:

This study of our means of exploration has shown that our resources do increase with the complexity of our subject. The two first methods of Observation and Experimentwe have seen to acquire a large extension in the case of this science while the third, before almost imperceptible, becomes, by the nature of the phenomena, wellnigh unbounded in its scope. We have next to examine the true rational position of Biology in the hierarchy of the fundamental sciences; that is, its relation to those that precede it, and to the one which follows it, in order to ascertain what kind and degree of speculative perfection it admits of, and what preliminary training is best adapted to its systematic cultivation. By this inquiry we shall see why

we are justified in assigning to it a place between chemistry and social science.

Relation of Bi- Of the relation of Biology to social science, ology to other I need say little here, as I shall have to speak sciences. of it at length in the next volume. My task will then be to separate them, rather than to establish their connection, which it is the tendency of our time to exaggerate, through the spontaneous development of natural philosophy. None but purely metaphysical philosophers would at this day persist in classing the theory of the human mind and of society as anterior to the anatomical and physiological study of individual man. We may therefore regard this point as sufficiently settled for the present, and pass on to the relation of Biology to inorganic philosophy.

It is to chemistry that Biology is, by its To Chemistry. nature, most directly and completely subordinated. In analyzing the phenomenon of life, we saw that the fundamental acts which, by their perpetuity, characterize that state, consist of a series of compositions and decompositions; and they are therefore of a chemical nature. Though in the most imperfect organisms, vital reactions are widely separated from common chemical effects, it is not the less true that all the functions of the proper organic life are necessarily controlled by those fundamental laws of composition and decomposition which constitute the subject of chemical science. If we could conceive throughout the whole scale the same separation of the organic from the animal life that we see in vegetables alone, the vital motion would offer only chemical conceptions, except the essential circumstances which distinguish such an order of molecular reactions. The general source of these important differences is, in my opinion, to be looked for in the result of each chemical conflict not depending only on the simple composition of the bodies between which it takes place, but being modified by their proper organization; that is, by their anatomical structure. Chemistry must clearly furnish the starting-point of every rational theory of nutrition, secretion, and, in short, all the functions of the vegetative life, considered separately; each of which is controlled by

RELATION OF BIOLOGY TO CHEMISTRY.

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the influence of chemical laws, except for the special modifications belonging to organic conditions. If we now bring in again the consideration, discarded for the moment, of the animal life, we see that it could in no way alter this fundamental subordination, though it must greatly complicate its actual application: for we have seen that the animal life, notwithstanding its vast importance, can never be regarded in biology otherwise than as destined to extend and perfect the organic life, whose general nature it cannot change. Such an intervention modifies, anew and largely, the chemical laws of the purely organic functions, so as to render the effect very difficult to foresee; but not the less do these laws continue to control the aggregate of the phenomena. If, for instance, a change in the nervous condition of a superior organism disturbs a given secretion, as to its energy or even its nature, we cannot conceive that such an alteration can be of a random kind: such modifications, irregular as they may appear, are still submitted to the chemical laws of the fundamental organic phenomenon, which permit certain variations, but interdict many more. Thus, no complication produced by animal life can withdraw the organic functions from their subordination to the laws of composition and decomposition. This relation

is so important, that no scientific theory could be conceived of in biology without it; since, in its absence, the most fundamental phenomena might be conceived of as susceptible of arbitrary variations, which would not admit of any true law. When we hear, at this day, on the subject of azote, such a doctrine as that the organism has the power of spontaneously creating certain elementary substances, we perceive how indispensable it still is to insist directly on those principles which alone can restrain the spirit of aberration.

Besides this direct subordination of biology to chemistry, there are relations of method between them. Observation and experimentation being much more perfect in chemistry, they serve as an admirable training for biological inquiry. Again, a special property of chemistry is its developing the art of scientific nomenclature; and it is in chemistry that biologists must study this important part of the positive method, though it cannot, from the complexity of their