science, be of so much scientific value as in chemistry. It is on the model of the chemical nomenclature that those systematic denominations have been laid down by which biologists have classified the most simple anatomical arrangements, certain well-defined pathological states, and the most general degrees of the animal hierarchy and it is by a continued pursuit of the same method that further improvements will be effected.

:

We thus see why biology takes its place next after chemistry, and why chemical inquiries constitute a natural transition from the inorganic to the organic philosophy. The subordination of biology to Physics follows from its relation to Chemistry: but there are also direct reasons, relating both to doctrine and method, why it should be so.

To Physics.

As to doctrine,—it is clear that the general laws of one or more branches of Physics must be applied in the analysis of any physiological phenomenon. This application is necessary in the examination of the medium, in the first place; and the analysis of the medium is required to be very exact, on account of the strong effect of its variations on phenomena so easily modified as those of the organism. And next, the organism itself is no less dependent on those laws, relating as they do to weight, heat, electricity, etc. It is obvious that if biology is related to chemistry through the organic life, it is related to physics by the animal life, -the most special and noble of the sensations, those of sight and hearing, requiring for the starting-point of their investigation an application of optics and acoustics. The same remark holds good in regard to the theory of utterance, and the study of animal heat and the electric properties of the organism. It remains to be wished that the biologists would study and apply these laws themselves, instead of committing the task to physicists: but they have hitherto followed too much the example of the physicists, who, as we have seen, have committed the application of mathematical analysis in their own science to the geometers; whereas, it cannot be too carefully remembered that if the more general sciences are independent of the less general, which, on the other hand, must be dependent on them, the students of the higher must be unfit, in virtue of that very independence,

RELATIONS TO PHYSICS AND ASTRONOMY.

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to apply them to a more complex science, whose conditions they cannot sufficiently understand. If the case was clear in regard to the intrusion of the geometers into physics, it is yet more so with regard to the intrusion of the physicists into biology; on account of the more essential difference in the nature of the two sciences. The biologists should qualify themselves for the application of the preceding sciences to their own, instead of looking to the physicists for guidance which can only lead them astray.

In regard to Method, biology is indebted to physics for the most perfect models of observation and experimentation. Observations in physics are of a sufficient complexity to serve as a type for the same method in biology, if divested of their numerical considerations, which is easily done. Chemistry however can furnish an almost equally good model in simple observation. It is in experimentation that biologists may find in physics a special training for their work. As the most perfect models are found in the study of physics, and the method is singularly difficult in physiology, we see how important the contemplation of the best type must be to biologists. Such is the nature of the dependence, as to doctrine and method, of biology on physics. We turn next to its relations with Astronomy; and first, with regard to doctrine.

To Astronomy.

The relation of physiology to astronomy is more important than is usually supposed. I mean something more than the impossibility of understanding the theory of weight, and its effects upon the organism, apart from the consideration of general gravitation. I mean, besides, and more specially, that it is impossible to form a scientific conception of the conditions of vital existence without taking into the account the aggregate astronomical elements that characterize the planet which is the home of that vital existence. We shall see more fully, in the next volume, how humanity is affected by these astronomical conditions; but we must cursorily review these relations in the present connection.

The astronomical data proper to our planet are, of course, statical and dynamical. The biological importance of the statical conditions is immediately obvious. No one questions the importance to vital existence of the mass of our

planet in comparison with that of the sun, which determines the intensity of gravity; or of its form, which regulates the direction of the force; or of the fundamental equilibrium and the regular oscillations of the fluids which cover the greater part of its surface, and with which the existence of living beings is closely implicated; or of its dimensions, which limit the indefinite multiplication of races, and especially the human; or of its distance from the centre of our system, which chiefly determines its temperature. Any sudden change in one or more of these conditions would largely modify the phenomena of life. But the influence of the dynamical conditions of astronomy on biological study is yet more important. Without the two conditions of the fixity of the poles as a centre of rotation, and the uniformity of the angular velocity of the earth, there would be a continual perturbation of the organic media which would be incompatible with life. Bichat pointed out that the intermittence of the proper animal life is subordinate in its periods to the diurnal rotation of our planet; and we may extend the observation to all the periodical phenomena of any organism, in both the normal and pathological states, allowance being made for secondary and transient influences. Moreover, there is every reason to believe that, in every organism, the total duration of life and of its chief natural phases depends on the angular velocity proper to our planet; for we are authorized to admit that, other things being equal, the duration of life must be shorter, especially in the animal organism, in proportion as the vital phenomena succeed each other more rapidly. If the earth were to rotate much faster, the course of physiological phenomena would be accelerated in proportion; and thence life would be shorter; so that the duration of life may be regarded as dependent on the duration of the day. If the duration of the year were changed, the life of the organism would again be affected: but a yet more striking consideration is that vital existence is absolutely implicated with the form of the earth's orbit, as has been observed before. If that ellipse were to become, instead of nearly circular, as eccentric as the orbit of a comet, both the medium and the organism would undergo a change fatal to vital existence. Thus the small eccentri

city of the earth's orbit is one of the main conditions of biological phenomena, almost as necessary as the stability of the earth's rotation; and every other element of the annual motion exercises an influence, more or less marked, on biological conditions, though not so great as the one we have adduced. The inclination of the plane of the orbit, for instance, determines the division of the earth into climates, and, consequently, the geographical distribution of living species, animal and vegetable. And again, through the alternation of seasons, it influences the phases of individual existence in all organisms; and there is no doubt that life would be affected if the revolution of the line of the nodes were accelerated; so that its being nearly immoveable has some biological value. These considerations indicate how necessary it is for biologists to inform themselves accurately, and without any intervention, of the real elements proper to the astronomical constitution of our planet. An inexact knowledge will not suffice. The laws of the limits of variation of the different elements, or, at least, a scientific analysis of the chief grounds of their permanence, are essential to biological investigation; and these can be obtained only through an acquaintance with astronomical conceptions, both geometrical and mechanical.

But,

It may at first appear anomalous, and a breach of the encyclopedical arrangement of the sciences, that astronomy and biology should be thus immediately and eminently connected, while two other sciences lie between. indispensable as are physics and chemistry, astronomy and biology are, by their nature, the two principal branches of natural philosophy. They, the complements of each other, include in their rational harmony the general system of our fundamental conceptions. The solar system and Man are the extreme terms within which our ideas will for ever be included. The system first, and then Man, according to the positive course of our speculative reason: and the reverse in the active process: the laws of the system determining those of Man, and remaining unaffected by them. Between these two poles of natural philosophy the laws of physics interpose, as a kind of complement of the astronomical laws; and again, those of chemistry, as an immediate preliminary of the biological.

Such being the rational and indissoluble constitution of these sciences, it becomes apparent why I insisted on the subordination of the study of Man to that of the system, as the primary philosophical characteristic of positive biology.

Though in the infancy of the human mind, when it was in its theological state, and in its youthful metaphysical stage, the order of these sciences was reversed, there was a preparation for the true view. Through all the fanciful. notions of the ancient philosophy about the physiological influence of the stars, we discern a strong though vague perception of some connection between vital and celestial phenomena. Like all primitive intuitions of the understanding, this one needed only rectification by the positive philosophy; under the usual condition, however, of being partially overthrown in order to be reorganized. But modern students, finding no astronomical conditions in the course of their anatomical and physiological observations, have discarded the idea of them altogether, as if it were ever possible for facts to bear immediate testimony to the conditions without which they could not exist, and which do not admit of a moment's suspension! Such an order of primitive conditions is however now established beyond dispute. In order to prevent any return to vicious or exaggerated notions about the physiological influence of the stars, it is enough to bear in mind two considerations: first, that the astronomical conditions of vital existence are comprised within our own planetary system; and secondly, that they relate, not directly to the organism, but to its environment, affecting as they do the constitution of our globe.

In regard to method, the importance of astronomical study to biologists consists, as in other cases, in its offering the most perfect model of philosophizing on any phenomena whatever; the importance of this example becoming greater in proportion to the complexity of the subordinate science, on account of the stronger temptation to discursive and idle inquiries offered by the latter. The more difficult their researches become, the more sedulous should physiologists be to refresh their positive forces at the source of positive knowledge; and, in the contemplation of the few