are by no means the seat of the soul, as held by certain authorities; these are only bridges of white substance that harmonize the functions of the two hemispheres which they connect; but here, moreover, we must not attach a meaning to words nor pretend to a decision not supported by the facts; as, for instance, is done by Treviranus, who asserts that the corpus callosum furnishes the brain with the faculty of comparisons, as if comparison were made between the thoughts. which come from the left and right, and not between impressions, or successive thoughts (Dugès).

The cerebral hemispheres, and especially their gray cortical substance, are the most essential portion of the brain. Here are accomplished the elaborations of the sensations in the form of thoughts. The experiments of Flourens, from which Longet especially has drawn legitimate conclusions, prove that animals from which the hemispheres have been removed, as we have before remarked in connection with the protuberance and tubercular quadrigemina, continue to feel, hear, see, and receive the impressions of taste; but that these impressions do not remain nor awake any response, nor seem to produce any associations of ideas; they do not look nor hear, nor smell, nor taste; in short, the cerebral lobes " are the receptacle where all sensations take a distinct form, and produce a continued remembrance." There may be a perfect sensation without the cerebral lobes; but this sensation bears a resemblance to that effect which is noticed in a person wrapt in profound meditation, and receiving an external irritation. (as, for instance, when a fly lights upon the hand), but whose meditation is not in any way interrupted, and who does not appear to notice the irritation (Vulpian, Taine).

On the other hand, the cerebral lobes preside over spontaneous movements. An attentive analysis of the movements of a frog or of a fish deprived of the cerebral lobes proves that these creatures swim only under the influence of reflex actions perfectly co-ordinated, which the impression of the water in contact with their integument may provoke; they progress as if impelled by a pre-established mechanism, as if subjected to a reaction which makes their progress an imperious necessity, until a new impression, as for instance coming in contact with the borders of the vessel or basin, causes the frog to assume a state of immobility and normal posture, a necessity no less imperious than the first. There are not seen in the behavior of the animal any of those capricious changes, or spontaneous movements from repose to activity

and vice versa, that characterize animals with uninjured cerebral lobes, and who hence are capable of volition or intentional spontaneity.

The faculties called intelligence and instinct unite these opposing phenomena, perception and thought on the one hand, volition and spontaneous movements on the other. The seat of the phenomena that we have just analyzed are localized in the cerebral hemispheres, especially in the gray cortical substance of these hemispheres. An animal deprived of these hemispheres is plunged in a peculiar sleep, dreamless sleep (Flourens). On the contrary, pathological conditions which over-excite the cerebral convolutions awaken in them chains of disordered thoughts, that a diseased brain considers external realities; of this order are the delirium in meningitis, madness in its acute and chronic varieties; thus those who are concerned in the care and study of insanity seek to attach to these organs the alterations of intelligence, especially the somatic element, in which psychical disturbances are simply the manifestation of the disease.

The development of the cerebral convolutions, and, perhaps we might even say, the quality of the gray cortical substance, are in proportion to the amount of intelligence possessed by the animal; idiots seem to have fewer nerve globules than persons of sound intellect. In the autopsy of idiots portions of the brain are found made up of connective tissue, and containing a large amount of embryonic globules which have not been transformed into nerve elements.1

D. GREAT SYMPATHETIC.

The great sympathetic is composed of a series of ganglions arranged along the side of the vertebral column (Fig. 15), at the side of each vertebra (except in the cervical region, where there are groups of three great ganglions). The ganglions of the same side are connected by commissures, whence result cords arranged in chaplets.

Moreover, these globular groups send commissures from one portion towards the spinal cord (rami communicantes), and from another portion towards the viscera and other organs in general (nerves of the great sympathetic). At a certain distance from the chain of the great sympathetic, in the course of those commissures, going either towards the

Küss in P. Ad. Rousseau. Thèse de Strasbourg, 1866. (Note "Sur le Rôle et l'Importance du Globule en Physiologie.)

spinal cord or the viscera, new ganglionic masses are found. Of this class numerous globular clusters are arranged like the rounds of a ladder on the nerves that return to the viscera. The most remarkable of these groups are the semilunar

Fig. 15.- Direction and general distribution of the great sympathetic nerve. (Dalton, "Human Physiology.")

ganglion, called by Bichat the abdominal brain. Finally, at a more distant portion in the path of the visceral nerves a new series of ganglions are distributed in the walls of the organs, being ordinarily only of microscopical dimensions.

Some of these occur in the tissue of the intestinal walls, in the muscular structure of the heart, in the bronchi, etc. (visceral or parenchymatous ganglions).

By means of these numerous ganglions or clusters of nerve globules, the sympathetic system seems to serve as a centre of certain reflex actions, as it possesses fibres having centrif ugal, and others having centripetal, properties. The great sympathetic has been considered the seat of all those nerve phenomena more or less mysterious that have been embellished with the name of sympathetic, and which we now call reflex phenomena. It must, however, be remembered that the great sympathetic is in no wise a system by itself; it simply shares in the properties and functions of the medullary system, and is associated with the latter.

In fact, its nerve fibres and filaments are excitable to the same agents as the spinal nerves, that is, to electricity and chemical agents; but the physiological excitant that we have previously designated by the name of volition or will has no effect upon this system; consequently, the movements which are produced in the department of the great sympathetic are all involuntary. On the other hand, those movements resulting from the artificial excitation of the nerve require a definite amount of time for their production. They are manifested slowly and cease slowly. This new difference has the same relation to the peculiar nature of the nervous and sympathetic fibres as in the case of the fibres of Remak (pp. 25 and 26), and of the muscles to which they are distributed (smooth muscles; see farther on). The excitation of the filaments of the great sympathetic gives also origin to the phenomena of sensibility, but an intense as well as long-continued irritation must be brought to bear upon them. In the pathological conditions the great sympathetic is much more excitable, and becomes both the seat and conductor of a large number of painful sensations. Formerly, too, the independence of this nervous system in its relations to the cerebro-spinal system was much exaggerated. It was made to preside as a central organ over the functions of the viscera in general, and more especially of those belonging to nutrition. Experiments by Cl. Bernard demonstrate that the sub-maxillary ganglion may serve as a centre for the salivary secretion; yet this result has lately been denied by Schiff1

Mau. Schiff, "Leçons sur la Physiologie de la Digestion," Vol. I., 12th Leçon.

The ganglions that occur in the wall of the viscera at the terminal branches of roots from the great sympathetic serve as a centre for partial movements of the visceral muscles, and regulate, by way of illustration, the peristaltic contractions of the intestinal walls. Other ganglions (of Wrisberg, semi-lunar, of the hypogastric plexus, etc.) might be considered as provisionary centres where the nervous action coming from a higher point can be accumulated. To-day the majority of the phenomena of the visceral functions have as their nervous centre the spinal cord, and even in the vasomotor functions (see circulation) the sympathetic has only a power of impression derived from the superior portion of the spinal axis. The same may be said in reference to its influence on the heart, and most of the visceral reflex actions whose centre is found in the spinal cord; so that the expression "great sympathetic system" has at this present time but little physiological signification.