and fine cylindrical white nerve-fibres, and with the gelatinous grey fibres. It may, therefore, be affirmed that every form of nerve-fibre in the ganglia is connected and continuous with the ganglionic cells.

Every ganglion thus possesses all the elements of a nervous centre, and the researches of physiologists tend to confirm the inference that such, in effect, is the case; and that each, in its own sphere, is capable of receiving, transmitting, originating, and reflecting impressions on which the healthy functions of the organs to which its nerves are sent depend.

The question relative to the manner in which nerves terminate is an exceedingly interesting one; and if the sympathetic nerve-fibres could be unequivocally traced to the special tissues wherein they end, a fair inference might be drawn as to their function. Some have been followed to their peripheral extremities by Dr. L. Beale, and he has described them as distributed over the walls of vessels. Dr. Tyson, of Pennsylvania, has endorsed his views; and Professor Eberth, of Zurich, has demonstrated the presence of nerves in the coats of all vessels, the capillaries excepted, even in the tunica adventitia of the non-muscular veins of the pia mater. And these, be it observed, partly consisting of dark-edged, and partly of pale fibres, which break up after they have penetrated the tunica adventitia into a fine net-work.*

There can be little doubt, however, that the sympathetic nerves also stand in intimate relation to the Stricker, op. cit., vol. i. p. 266.

secreting cells of glands. Their distribution in the salivary gland has been described by Pflüger.* In this organ the dark-edged or medullated nerves constitute the greater number and accompany the salivary tubes, perforate the membrana propria, then divide into innumerable fibrils, each of which becomes continuous with a salivary cell. The pale or non-medullated nerves are composed of extraordinarily fine fibrils, each of which is continuous with the fibrillated substance of the epithelial cells.

The axis-cylinder which invests these pale fibres, is found to be continuous with the membrana propria.

Such being the anatomical relationship subsisting in the so-called sympathetic system of nerves, much circumspection is necessary in drawing conclusions from experiments, seeing that the cerebro-spinal nerves are intimately commingled with the nerves of Remak, all running parallel to each other.

I may observe, incidentally, that such compound nerves appear to fulfil all the conditions which are said to be necessary for what is called electro-tonus (a state whereby one nerve is rendered active by the activity of another in close proximity with it), and many phenomena which I may have to adduce seem to point to such influence; but I shall endeavour to confine my remarks to such experiments and observations as have reference to single nerves only.

This, however, can be done in no other way than by comparing the phenomena induced and presented by the cerebro-spinal nerves alone, with such other phenomena as are produced by the special agency of

the fibres of Remak, and by investigating in what respect the mode of action of the one set differs from that of the other; for we may assume that Nature is too good an economist to endow the fibres of one with attributes possessed by the other, when included in the same nerve.

It is very probable that all may be in some degree modified, and it is difficult to conceive why the ganglionic cells are the connecting media between the three sets of nerves, if some change of function be not the result. In illustration of this, the sensory nerves appear to lose much of their peculiar sensibility, as we recognise it in their ordinary impressions on the brain, when they proceed from an organ to a ganglionic centre of the sympathetic system; and if so, it follows that, by virtue of the reciprocal action which sensitive and motor nerves exercise on each other, and on the organs to which they are distributed, the motor fibres must be invested with properties derived from the modified sensitive

nerves.

What, then, is the special function of each dif ferent form of nerve-fibre respectively which goes to or proceeds from every ganglionic centre?

With the view to an explicit answer to this question, the most obvious method is to select from the three forms of nerve-fibre the single one which is invariably associated with a peculiar phenomenon, and without which that phenomenon does not occur. The logical "method of difference," in effect, is that which I shall endeavour to pursue.

ON THE FUNCTIONS OF THE SYMPATHETIC SYSTEM OF NERVES.

IN M. Claude Bernard's experiments on the sympathetic nerves, the results of which he communicated to the French Academy,* the interesting fact was educed, that whenever the sympathetic nerve in the neck of a rabbit is divided, an elevation of temperature occurs in the tissues on the corresponding side of the head, amounting to 7° Fahr. when contrasted with the uninjured side. This increase of heat was plainly perceptible by the hand, and admitted of accurate measurement by the introduction of the bulb of a thermometer within the nostril, or into the external auditory meatus. The whole body shared, to a certain extent, in this development of heat, and exhibited evidence of a temperature exceeding the natural standard; but it was most evident on the side of the neck where the sympathetic had been divided, and least so on the opposite side where it had been left uninjured. The mercury rose to 72° Fahr. on the affected side, but only to 68° on the uninjured side. Nor was this elevation a transitory phenomenon, for it continued with remarkable steadiness until the animal was killed, and even after death the side of the neck on which the experiment was practised was the last part of the body to lose its vital heat. In some other cases the increased heat disappeared, but in

Comptes Rendus, vol. xxxiv. p. 472. Fevrier, 1852.

no instance was there oedema, nor any morbid phenomenon resembling inflammation.

In addition to the above phenomena, M. Bernard subsequently noticed an increased temperature of the cerebral hemispheres, as well as of the blood itself in the internal jugular vein on the side in which the sympathetic nerve had been divided.*

Schiff has repeated these experiments, and infers, from precisely the same results, that active dilatation is a function possessed by blood vessels.

Dr. W. Ogle communicated to the Royal Medical and Chirurgical Society the history of a suppurating tumour in the neck of a man, which produced lesion equivalent to a division of the cervical sympathetic. In this case the ear on the affected side was redder and warmer by two degrees Fahrenheit, than that on the opposite side, and there was a total cessation of cutaneous secretion on the right (affected) side of the face, head, and neck, although the skin of the right cheek was pinker than that of the left.

We may infer, then, that the disseverance of the minute arteries from the influence of the nerves of Remak is productive of increased vascularity, and an elevation of the temperature of the parts so disconnected.

M. Claude Bernard exposed in a dog the gustatory nerve, the chorda tympani (before they receive communicating branches from the lingual nerve), and the submaxillary ganglion. Having thus before him a sensory nerve, a motor nerve, and a ganglio

* Mémoires de la Société de Biologie. 1853.

+ Medico-Chirurgical Transactions, vol. lii. p. 151. 1869.