of apology for the promulgation of the hypothesis,14 that at the period when its author wrote, he could not present his facts with any hope of being attended to, if he did not connect them by some common tie, some dominant idea which might gratify the mind; and that, acting under this necessity, he did well to substitute for the extant theories, already superannuated and confessedly imperfect, conjectures more original and more probable. Without dissenting from this view, we may observe, that Buffon's theory, like those which preceded it, is excusable, and even deserving of admiration, so far as it groups the facts consistently; because in doing this, it exhibits the necessity, which the physiological speculator ought to feel, of aspiring to definite and solid general principles; and that thus, though the theory may not be established as true, it may be useful by bringing into view the real nature and application of such principles.

It is, therefore, according to our views, unphilosophical to derive despair, instead of hope, from the imperfect success of Buffon and his predecessors. Yet this is what is done by the writer to whom we refer. 'For me,' says he,15 'I avow that, after having long meditated on the system of Buffon,-a system so remarkable, so ingenious, so well matured, so wonderfully connected in all its parts, at first sight so probable;— I confess that, after this long study, and the researches which it requires, I have conceived in consequence, a distrust of myself, a skepticism, a disdain of hypothetical systems, a decided predilection and exclusive taste for pure and rational observation, in short, a disheartening, which I had never felt before.'

The best remedy of such feelings is to be found in the history of science. Kepler, when he had been driven to reject the solid epicycles of the ancients, or a person who had admired Kepler as M. Bourdon admires Buffon, but who saw that his magnetic virtue was an untenable fiction, might, in the same manner,

14 Bourdon, p. 221.

15 Ib. p. 274.

have thrown up all hope of a sound theory of the causes of the celestial motions. But astronomers were too wise and too fortunate to yield to such despondency. The predecessors of Newton substituted a solid science of Mechanics for the vague notions of Kepler; and the time soon came when Newton himself reduced the motions of the heavens to a Law as distinctly conceived as the Motions had been before.

CHAPTER V.

EXAMINATION OF THE NERVOUS SYSTEM, AND CONSEQUENT SPECULATIONS.

Sect. 1.-The Examination of the Nervous System.

produced conjectural and hypothetical attempts to connect structure and action with some higher principle, of a more peculiarly physiological kind. But it may still be instructive to notice a case in which the principle, which is thus brought into view, is far more completely elevated above the domain of matter and mechanism than in those we have yet considered;-a case where we have not only Irritation, but Sensation; -not only Life, but Consciousness and Will. A part of science in which suggestions present themselves, brings us, in a very striking manner, to the passage from the physical to the hyperphysical sciences.

We have seen already (chap. i.) that Galen and his predecessors had satisfied themselves that the nerves are the channels of perception; a doctrine which had been distinctly taught by Herophilus in the Alexandrian school. Herophilus, however, still combined, under this common name of Nerves, the Tendons; though he distinguished such Nerves from those which arise from the brain and the spinal marrow, and which are subservient to the will. In Galen's time this subject had been prosecuted more into detail. That anatomist has left a Treatise expressly upon The Anatomy of the Nerves; in which he describes the successive Pairs of Nerves: thus, the First Pair are the visual nerves: and we see, in the language which

1 Spr. i. 534.

Galen uses, the evidence of the care and interest with which he had himself examined them. These nerves,' he says, 'are not resolved into many fibres, like all the other nerves, when they reach the organs to which they belong; but spread out in a different and very remarkable manner, which it is not easy to describe or to believe, without actually seeing it.' He then gives a description of the retina. In like manner he describes the Second Pair, which is distributed to the muscles of the eyes; the Third and Fourth Pairs, which go to the tongue and palate; and so on to the Seventh Pair. This division into Seven Pairs was established by Marinus,2 but Vesalius found it to be incomplete. The examination which is the basis of the anatomical enumeration of the Nerves at present recognized, was that of Willis. His book, entitled Cerebri Anatome, cui accessit Nervorum descriptio et usus, appeared at London in 1664. He made important additions to the knowledge of this subject.3 Thus he is the first who describes in a distinct manner what has been called the Nervous Center, the pyramidal eminences which, according to more recent anatomists, are the communication of the brain with the spinal marrow and of which the Decussation, described by Santorini, affords the explanation of the action of a part of the brain upon the nerves of the opposite side. Willis proved also that the Rete Mirabile, the remarkable net-work of arteries at the base of the brain, observed by the ancients in ruminating animals, does not exist in man. He described the different Pairs of Nerves with more care than his predecessors; and his mode of numbering them is employed up to the present time. He calls the Olfactory Nerves the First Pair; previously to him, these were not reckoned a Pair: and thus the optic nerves were, as we have seen, called the first. He added the Sixth and the Ninth Pairs, which the anatomists who preceded him did not reckon. Willis also examined carefully the different Ganglions, or knots which occur upon the nerves. He traced them wherever they were to be found, and he gave a general

2 Dic. Sc. Med. xxxv. 467.

3 Cuv. Sc. Nat. p. 385.

4 Ibid.

figure of what Cuvier calls the nervous skeleton, very superior to that of Vesalius, which was coarse and inexact. Willis also made various efforts to show the connexion of the parts of the brain. In the earlier periods of anatomy, the brain had been examined by slicing it, so as to obtain a section. Varolius endeavoured to unravel it, and was followed by Willis Vicq d'Azyr, in modern times, has carried the method of section to greater perfection than had before been given it; as Vieussens and Gall have done with respect to the method of Varolius and Willis. Recently,

Professor Chaussier makes three kinds of Nerves:the Encephalic, which proceed from the head, and are twelve on each side; the Rachidian, which proceed from the spinal marrow, and are thirty on each side;— and Compound Nerves, among which is the Great Sympathetic Nerve.

One of the most important steps ever made in our knowledge of the nerves is, the distinction which Bichat is supposed to have established, of a ganglionic system, and a cerebral system. And we may add, to the discoveries in nervous anatomy, the remarkable one, made in our own time, that the two offices-of conducting the motive impressions from the central seat of the will to the muscles, and of propagating sensations from the surface of the body and the external organs of sense to the sentient mind-reside in two distinct portions of the nervous substance:—a discovery which has been declared to be 'doubtless the most important accession to physiological (anatomical) knowledge since the time of Harvey.' This doctrine was first published and taught by Sir Charles Bell: after an interval of some years, it was more distinctly delivered in the publications of Mr. John Shaw, Sir C. Bell's pupil. Soon afterwards it was further confirmed, and some part of the evidence corrected, by Mr. Mayo, another pupil of Sir C. Bell, and by M. Majendie.8

5 Cuv. p. 40.

6 Dict. Sc. Nat. xxxv. 467.

8 As authority for the expres sions which I have now used in

7 Dr. Charles Henry's Report of the text, I will mention Müller's

Brit. Assoc. iii. p. 62.

Manual of Physiology, (4th edition,