But the interest which we have felt in the progress of this great man now begins to be less intense. He seems to us to have accomplished his destiny, and we prepare to trace his steps to the grave. In his domestic life he is supposed to have been subjected to many mortifications, arising from the parsimony and domineering temper of his wife. Long before this period, too, he had become subject to attacks of rheumatism, gravel, and gout; while his too-sensitive mind was harassed by the open as well as more insidious attacks of his opponents. It is pleasing to witness the reconciliation of enemies, and we have already remarked that Linnæus and his old antagonist Rosen were ultimately on the most friendly terms. "In 1764," says the private manuscript, "he was attacked by a violent pleurisy. He was anxiously attended by Dr Rosen, who saved him from certain death. From this time he conceived the most sincere affection for his brother-professor."
Before proceeding to convey the prince of naturalists to the tomb, it seems expedient to examine the most important of his numerous works,—that, namely, in which he arranges all the known objects of nature, and of which the last edition, brought out under his own inspection, appeared about this epoch of his life.
SECTION VIII.
Account of the Systema Naturæ of Linnæus.
Linnæus's Classification of the Animal Kingdom—Remarks on the Gradations employed, and on Nomenclature—Classification of the Animal Kingdom—General Remarks—Method of Tournefort—Method of Linnæus—Classification of the Vegetable Kingdom—Theory of the Formation of Minerals and Rocks.
The work just mentioned bears the title of Systema Naturæ per Regna tria Naturæ, secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis,—A System of Nature, in which are arranged the objects constituting the three kingdoms of nature, in classes, orders, genera, and species, with their characters, differences, synonymes, and places of occurrence.
The first volume contains the animal kingdom. The introduction presents a brief view of the constitution of the world, in the usually laconic style of the author. In it the three kingdoms of nature are thus defined:—Minerals are concrete bodies, possessing neither life nor sensibility; vegetables are organized bodies, possessed of life, but without sensibility; animals are organized bodies, possessing life and sensibility, together with voluntary motion. Objections may be made to these definitions; but it is not our object at present to criticise his views and arrangements, our intention being simply to offer a brief account of them, omitting all that is not absolutely essential. It ought to be understood, that the entire work is merely an index or catalogue of the productions of nature; that it was obviously intended as such by its author; and that they who object to the Systema Naturæ, because it contains nothing more than characteristic notes methodically arranged, forget that Linnæus never professed to give descriptions in it.
The natural division of animals, he says, is indicated by their internal structure. This principle his modern adversaries have chosen to overlook, asserting that his classification is founded on external form. In some species the heart has two distinct cavities, and the blood is warm and red; of these some are viviparous,—the mammalia,—others oviparous,—the class of birds. In certain species the heart has only a single cavity, with a single auricle, the blood red but cold; of these the amphibia have a voluntary respiration, while fishes respire by gills. In other animals the heart has also a single cavity, but without an auricle, while the blood is cold and of a white colour; of these the insects are characterized by their antennæ, the vermes or worms by their tentacula.
The Mammalia, which constitute the first class, are the only animals furnished with teats. Their clothing, hoofs, claws, horns, teeth, and other organs, are briefly described, in such a manner as to enable the student to comprehend the meaning of the terms to be subsequently employed. The characters of the orders are derived principally from the teeth.
I. Primates or Nobles: Mammalia furnished with fore teeth, of which there are four in the upper jaw, and two pectoral mammæ.