secondary tissues, the first consideration is of the general position, which is always related to a modification, greater or smaller, of the structure itself. Comparative analysis shows us that in the case of both the muscular and the nervous system, the organization of the tissue becomes more special and elevated, exactly in proportion to its deeper position between the exterior and interior surfaces of the animal envelope. Thence arises the rational division of each of these systems into superficial and profound. This distinction is more especially remarkable with regard to the nervous system, arranged, first, in the form of filaments, and afterwards that of ganglions, with or without external apparatus.

This is the family of tissues, the study of which forms the basis of anatomical analysis. It would be departing from my object to inquire into the laws of composition under which the ascent is made from this primary study to that of porous substances, and thence on to the theory of the organs, and then to that of systems of organs, which would lead us on to physiological analysis. I have fulfilled the aim of this section in exhibiting the methodical connection of the four degrees of anatomical speculation, about which no real uncertainty exists.

Limitation of the inquiry.

Deeper than this we cannot go. The last term in our abstract, intellectual decomposition of the organism is the idea of tissue. To attempt the passage from this idea to that of molecule, which is appropriate to inorganic philosophy, is to quit the positive method altogether: and those who do so, under the fancy that they may possibly establish a notion of organic molecules, and who give that vain search the name of transcendental anatomy, are in fact imitating the chemists in a region into which Chemistry must enter in its own shape where admissable at all, and are asserting in other words that, as bodies are formed of indivisible molecules, animals are formed of animalcules. This is simply an attempt, in the old spirit, to penetrate into the nature of existences, and to establish an imaginary analogy between orders of phenomena which are essentially heterogeneous. It is little creditable to the scientific spirit of our time that this aberration should call for exposure and

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rebuke, and that it should need to be asserted that the idea of tissue is, in organic speculation, the logical equivalent of the idea of molecule in inorganic speculation.

We here find ourselves in possession of a sufficient basis of anatomical science, while we need yet a more complete and profound combination of the ideas of comparative and textural anatomy. This want will be supplied when we become universally familiarized with the four analytical degrees, complementary to each other, which must henceforth be recognized and treated as the basis of anatomical speculation.

CHAPTER III.

BIOTAXIC PHILOSOPHY.

AFTER the anordination of all known, or even FTER the statical analysis of living bodies, there must possible organisms, in a single series, which must serve as a basis for the whole of biological speculations. The essential principles of this philosophical operation are what I have now to point out.

Comparative anatomy of

animals.

We have already seen that it is the distinction of biological science to have devegetables and veloped the theory of classifications, which, existing in all sciences, attains its perfection when applied to the complex attributes of the animal organisms. In all ages, the vegetable organism was the direct subject of biological classification; but it was pursued on the principles furnished by the consideration of animals, whence the type was derived which guided philosophical speculation in the case. It could not be otherwise, so marked and incontestable as are the distinctions among animal organisms: and even the zoological classification of Aristotle, imperfect as it is, is infinitely superior to anything which could then have been attempted with regard to vegetables. This natural original classification has been rather rectified than changed by the labours of modern times; while that of vegetables has met with an opposite fate. As a fact, the first successful attempts in the animal region long preceded the establishment of the true principles of classification; whereas, it was only by a laborious systematic application of these principles that it has been possible, even within a century, to effect any rational co-ordination in the vegetable region, so little marked, in comparison, are the distinctions in the latter The natural result was that the animal realm, used as a type, became more and more attended to, till the

case.

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61

improvements in zoological classification have gone so far as perhaps to lead us to fear that the vegetable organism, owing to its great simplicity, can never become subject to a much better classification than that in which it was left in the last century. The labours of the reformers of that time are very far indeed from having been useless; only, what they undertook for the vegetable kingdom has turned rather to the profit of the animal;—an inevitable circumstance, since the property which rendered the animal kingdom the natural type of the taxonomical series must adapt it to receive all the improvements arising from the general principles of the theory. The character of the theory could not but remain incomplete, however, as long as the vegetable classification continued to be regarded as the chief end of the research; and the classification became rational only when it was seen that the vegetable region was the further end of the series, in which the most complex animal organism must hold the first place; an order of arrangement under which the vegetable organism will be more effectually studied than it ever was while made an object of exclusive investigation. All that is needed is that naturalists should extend to the whole series the anatomical and physiological considerations which have been attached too exclusively to animal organisms; and this will certainly be done now that the human mind is fairly established at the true point of view, commanding the fundamental theory of natural classification.

These prefatory remarks indicate our Animal anatheme. We must have the whole series in tomy our subview; but the animal region must be our ject. immediate and explicit subject, both as furnishing the rational bases of the general theory of classification, and as exhibiting its most eminent and perfect application.

Division of the natural method.

The subject divides itself into two parts: the formation of natural groups, and their hierarchical succession ;- -a division necessary for purposes of study, though the two parts ultimately and logically coalesce.

In contemplating the groups, the process is to class together these species which pre

Natural groups.

sent, amidst a variety of differences, such essential analogies as to make them more like each other than like any others, without attending, for the present, to the gradation of the groups, or to their interior distribution. If this were all, the classification must remain either doubtful or arbitrary, as the circumscription of each group could seldom be done so certainly as inevitably to include or exclude nothing that might not belong to another group: and great discordance was therefore observed in the early division into orders, families, and even genera. But the difficulty disappears on the foundation of the fundamental hierarchy, which rigorously assigns its place to each species, and clearly defines the ideas of genera, families, and classes, which henceforth indicate different kinds of decomposition, effected through certain modifications of the principle which graduates the whole series. The animal realm, especially in its higher parts, is as yet the only one in which the successive degrees have admitted a fully scientific description. The rough classification into natural groups was an indispensable preparation for the marshalling into a series of the immeasurable mass of materials presented by nature. The groups being thus separated, and the study of the irinterior distribution postponed, the innumerable throng of organic existences became manageable. This great benefit has misled botanists into the supposition that the formation of these groups is the most scientific part of the natural method, otherwise than as a preliminary process. The regular establishment of natural families offers, no doubt, great facilities to scientific study, by enabling a single case to serve for a whole group: but this is a wholly different matter from the value of the natural method, regarded as it must henceforth be, as the highest rational means of the whole study, statical and dynamical, of the system of living bodies; and the great condition of which is that the mere position assigned to each body makes manifest its whole anatomical and physiological nature, in its relation to the bodies which rank before or after it. These properties could never belong to any mere establishment of natural families, if they could be grouped with a perfection which is far from being possible; for the

Co-ordination

of them.