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.

PART THIRD.

CONTRACTILE ELEMENTS.- MUSCLE AND ITS

ADJUNCTS.

I. MUSCLES IN GENERAL.

THE muscular elements are produced by metamorphosis of the globules of the embryo. By studying their formation we may best understand the three types presented by the muscular system, -the contractile cell, smooth fibre, and striated fibre. We notice, at the same time, that the property of changing their shape (or contractility), which is characteristic of these different kinds of muscles, is only the same property, carried to a higher degree, which we have ascertained belongs to globules in general.

When an embryonic globule is slightly lengthened, and its nucleus becomes more visible, etc., we have the contractile cell (Fig. 16, 1), as it is found, for instance, in the smaller arteries.

When the cells are united at the ends in such a way as to form a varicose fibre, with elongated nuclei in different parts, and granular contents,

3

we have the smooth fibre, in which, Fig 16.- Diagram of the three moreover, are found all the elements of the cell (Fig. 16, 2).

forms of the contractile or muscular element *

Finally, as the fibre straightens, and the fusion of the cells. becomes complete, we have the striated fibre (Fig. 16, 3), the

* 1, Contractile cell. 2, Smooth muscle. 3, Striped muscle.