IIaving thus brought to a termination our review of the physiology of the encephalon, I may now sum up the principal conclusions which our examination of this difficult and im portant subject leads to; and these are embraced in the following propositions.
I. That the encephalon consists of a series of centres, each of which has its proper influ ence in the exercise of the mental and bodily functions. These are the centre of intellectual actions, the centre of volition, the centre of sensation, the centre of the coordination of muscular movements, the centre of eniotion, and the centre of respimtion and of deglutition.
2. That the cerebral convolutions, with the fibres which connect them to the corpora striata and optic thalami, constitute the centre of intel lectual action.
3. That the centre of volition consists prima rily `of the corpora striata ; the inferior layers of the crum cerebri, which are continuous with the anterior pyramids, connect these gangliform bo dies with the vesicular matter of the crura (locus niger), with the vesicular matter of the mesoce pliale, medulla oblongata, and with that of the spinal cord (the anterior horns), all of which with the corpora striata probably form the dynamic nervous matter in the impulses of volition for nerves implanted in them respectively.
4. The optic thalami, which by the extension of the olivary columns through tile mcsocephale and medulla oblongata to the posterior horns of the vesicular matter of the spinal cord, become-continuous with those parts, constitute the centre of sensation, havi»g implanted in it or connected with it less directly all the sentient nerves of the body.
The nerves of the higher senses probably have each special ganglia or centres, which, however, are connected with the general centre; as the olfactory lobes for smell; the retina, corpora geniculata, or corpora quadrigernina for vision ; the vesicular matterin which the auditory nerves are implanted or the flocks of Reil for hearing; the ganglia of the fifth, glosso-pharyngeal, and posterior roots of spinal nerves for taste and touch.
5. The cerebellum constitutes the centre of the coordination of muscular movements, both in locomotion and in all the complicated move ments of the frame.
6. The upper and posterior part of the me soeephale, including probably the greatest por tion of the corpora quadrigemina, constitutes a special centre of actions referable to the emo tions, among which may be reckoned sexual impulses. This centre connects itself with the
medulla oblong,ata by the olivary columns, and through the same channel with the -posterior horns of the spinal vesicular rnatter.
7. The medulla oblongata constitutes the centre of respiration and deglutition, but it cannot be considered as wholly devoted to these functions, inasmuch as it consists like wise of continuations of the centres of volition, of sensation, and of emotion.* Of the functions of the ganglions.—That ganglions are small nervous centres we are bound to believe, from the existence in them of a considerable quantity of vesicular matter min gled with fibrous matter. And the views which we have already expressed respecting the dy namic character of the vesicular matter warrant the assumption that wherever a special accumu lation of that form of nervous matter is found, there must be a special source of nervous power.
There are certain facts connected with the larger nervous centres.which strongly indicate the correctness of this assumption. Thus, the existence of special accumulations of vesicular matter connected with them, where any parti cular development of the nervous force is needed, is much in favour of this view. As instances, we may cite the special electrical lobes in the electrical fishes, the ganglionic en largements on the medulla oblongata of the gurnard, the median lobe, occupying a. similar position to the electrical lobe above referred to, which is found in the remora or sucking fish, and from which nerves are supplied to the suctorial disc on the head of that animal. Allied to these is the remarkable fact pointed out by Professor Sharpey, that the arms of the cuttle-fish contain ganglia which furnish nerves to the suckers which exist upon them in great number. Furthermore, the anatomy of the nervous system in some of the Mollusca, the Conchifem for example, in which a separate ganlion appears to exist for each function, for respiration, for locomotion, for deglutition, &c., is beautifully illustrative of the office of ganglia.