carbonic acid gas, with the additional one of nitrogen, which peculiarly belongs to this kingdom, and the volatile nature of which perfectly agrees with the rapid merging of animal bodies in the universal life of nature, as soon as their individual life is extinct; to which passage, however, the earthy parts, such as bones and shells, offer somewhat longer resistance. In regard to the internal formation of the solid parts of the animal body, it has been already remarked (see p. 244) that the spherical type, in so far as it is peculiar to animal forms in general, is also visible in the basis of all animal matter, so that the molecular substance is the basis of the collective animal body. If we now reflect likewise how in the Infusoria and Priestley's matter, the rudiments of the animal kingdom appear as so many animated globuli, we shall thence perceive that the largest animal bodies themselves must be viewed as an innumerable aggregate of Infusoria, but at the same time united into a living whole. It is moreover worthy of remark, that very essential differences present themselves in respect to the primary formation of the animal body in its different systems. It is also a remarkable fact, that in the organs exclusively proper to the animal,—for instance, in those of sense, motion, and the nerves,—this molecular mass is clearly discernible, partly as the marrow of the nerves (a peculiar grey substance), partly as developed nervous and muscular fibres; while in the organs which are more immediately borrowed from the plant (the vascular system, the skin, and the intestines), we remark again a very decided tendency to cellular formation.
We have now before us two modes of perceiving in its true nature the further formation of the primary animal mass into the single organs of the animal body; either that of attentively watching the development of one complete animal organism in its different stages, or that of observing the succession of the species according to the order of animals in the development of their animalism. Of these two we shall give only the principal outlines of the first series of formation[1], in which we shall find a great analogy to the development of the plant, but more especially a manifold confirmation of that which we have advanced in regard to the metamorphosis, or rather elevation, of vegetable into animal life. But in tracing the development of the individual animal body through its several stages, we shall take as the main object of our observations the human organization as the most perfect; and thus we shall have occasion to recur to that of other animals in those cases only in which the observations made on the human being itself are deficient in regard to its first rudiments.
- ↑ The observation of the development of organization in the series of animals, is the idea upon which Carus's Manual of Zootomy is founded, to which he here refers his readers.
