For example, we have cause to suppose that there is in infancy a progressive education of the organs of sense, correcting the original perceptions they afford; defining the relations of the several senses; and giving unity of effect to impressions made on double organs. In like manner the education of the voluntary powers may be said not merely to extend the influence of the will to new muscular movements, but also to concentrate and individualise the powers of the mind in acts of volition, separating them more entirely from the involuntary actions of the same parts. And carrying the argument further, we may suppose that the faculties of memory and combination are subject to the like education; tending always to give more proper and perfect unity to these functions than belongs to them in the outset of life, and to establish more completely the conscious individuality of the being.

This view, if just in itself, is fertile in curious inferences, and serves better than any other to conciliate the phenomena of infancy with those of advancing age; the progress from confused, or it may be double perceptions, - from automatic or ill-regulated motions, from imperfect and confused associations and impotence of recollection, to that singleness of perception, volition, and memory which the mind attains in its healthy state, and which marks the intellectual character of man. This, however, is one of the many points at which human reason is forced to pause, before entering on paths too obscure for its further progress.

In the foregoing remarks I have spoken generally of the brain as a double organ, without referring to the several parts of this complicated structure; or to the effects of morbid changes upon these respectively, in altering the relation of the two sides, and the functions which are perfect only from their entire correspondence. The excuse for this want of detail must be found in the very incomplete knowledge

we yet possess on the subject. Notwithstanding all that has been obtained from comparative anatomy, pathology, and actual experiment (and large has been of late years the gain from all these sources), there is still scarcely a single part in the structure of the great nervous centres composing the brain, in which we can affirm with certainty the connexion between particular function and portion of structure. The inferences drawn with seeming assurance from one experiment or pathological fact have been as expressly negatived by others. In a few instances such as the general facts that the lobes of the cerebrum have more express relation to the mental faculties; that the organs of speech depend on the anterior lobe; the motions of respiration on the corpora olivaria; the senses of sight, hearing and smell, on certain tubercles or ganglia proper to each approach has been made to more certain knowledge; but still not without much ambiguity, arising from the complex nature of the functions themselves, as well as of the disturbing causes from which inferences are drawn. In the case of vision, for example, we have the perplexing fact of blindness, more or less complete, produced by injuries to remote and seemingly unconnected parts of the brain, and even by affections of the spinal marrow and similar contrarieties exist as to other senses and functions.

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One of the most singular proofs how much is wanting to our knowledge of the brain, may be found in the fact, that we are yet ignorant, or at least not assured, of the true functions of the cerebellum; -a part which, from its size, situation, and structure, must be judged to fulfil some one or more of the most important purposes in our being. That it is a source. of, or determines the distribution and agency of some particular nervous power, may be deemed certain; but the contradictory opinions or confessed ignorance of the most eminent physiologists, as to the nature and actions of this

power, denote it as a remarkable object of discovery still unattained.*

That our knowledge of the respective functions of the cortical and medullary parts of the brain and spinal cord should be still mere surmise, is another striking proof how much we have to gain on this subject. We can affirm almost with certainty that the functions must be different; but whether the first be a structure for generating power, the second for conveying it; - or whether, as others have supposed, the cineritious part has to do with motive power, the medullary with sensation and volition ; - or whether the distinction is to be sought for in some less obvious source; - are questions yet open, the solution of which will singularly enlarge our knowledge in every part of physiology.

In treating thus generally of the brain under its condition as a double organ, there has been no occasion to refer to the doctrines of phrenology. This system indeed, in recognising separate organs, perfectly alike and equivalent to each other, in each hemisphere, is bound more especially to suppose that any casual disparity between the corresponding organs of the two sides must have effect in disordering the faculties therewith connected. But the course of argument just pursued

* Even the minute and delicate anatomy of Reil has failed of reaching this discovery. The inferences derived in common from the researches of Majendie, Flourens, and Hertwig, though still subject to dispute, are probably those which approach nearest the truth, notwithstanding some recent experiments in Germany, which have the aspect of being more favourable to Gall's view of the cerebellum. Seeing the uncertainty which hangs over this subject, there is much interest in the late discovery by Mr. Solly of direct nervous communication, through the restiform bodies, between each lobe of the cerebellum and the sentient and motor nerves of the same side. And to the researches of Sir Charles Bell, fruitful of so many great discoveries, we owe much that bears upon this obscure point in physiology.

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is independent of these particular assumptions. And, while seeking to afford a foundation whereon to rest further knowledge of these parts, it does not profess more than to trace one great condition of the cerebral structure that of doubleness of parts into some of its probable effects on the sensorial functions and the general economy of life.

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CHAP. XIII.

ON SOME POINTS IN THE PATHOLOGY OF THE COLON.

I DOUBT Whether all the functions and disorders of this bowel have obtained proper attention in practice, or their influence in producing disorder elsewhere been sufficiently regarded. The colon is often viewed merely as a part of the alimentary canal, with the office of simple transference through it, after the more important stages of digestion have been completed. It is certain, however, that there is much beyond this, in its actions both of healthy and morbid kind. Its peculiar situation, connexions, and flexures; the great extent of internal surface, multiplied by the bands, folds, and other inequalities of the lining membrane; - its liability to unequal distension, contraction, or stricture;-and the variety of secretions from the glands and vessels of its inner surface; -all concur in giving great importance to this intestine in the animal economy. From its continuity with the rectum, many circumstances are common to the two portions of the canal, and to these the following remarks will equally apply. But each part has its peculiarities; and those of the colon, for obvious reasons, have hitherto engaged less than their relative share of notice.

The nature and amount of change in the alimentary matters, as they pass through this part of the canal, are yet not wholly known; nor are we assured as to the opinion lately propounded, on the authority of Dupuytren and other accurate observers, that the large intestines are peculiarly con