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determined in the gland by the tympano-lingual and the sympathetic nerve, are diametrically opposite.

When the tympano-lingual nerve is excited, the venous blood appears red, and at the same time there supervenes a considerable exaltation in the rapidity of the circulation. In proportion as the venous blood becomes more red, it circulates more and more rapidly, and the quantity which flows through the vein becomes manifestly greater. To give an idea of this difference, it will suffice to report that, in a case where we measured the blood which issued from the glandular vein, we found, during the repose of the gland, while the blood flowed black, it took seventyfive seconds to obtain five cubic centimeters; but while the tympanolingual nerve was in action, and the blood escaped red, under the influence of the galvanism of this nerve, it took no more than fifteen seconds to obtain this quantity of blood, which proves that the circulation in the latter case was four times more rapid than in the former.

When the great sympathetic acts, it renders the venous blood black, and we see the circulation become slower at the same time; the blood flows through the vein in quantity the less abundant the blacker the blood appears; and, indeed, if the action of the sympathetic nerve is sufficiently energetic, the sanguine current can be arrested altogether in the vein, to reäppear when the irritation of the sympathetic ceases, and to become rapid again if irritation be applied to the tympano-lingual nerve.

These results, then, which are constant, apprise us that the black or red color of the venous blood has a determinate relation with the rapidity of the circulation in the submaxillary gland. But this rapidity of the blood-stream itself cannot be effected directly by the nerves, which can in no case act directly upon the blood; the constrictions and dilatations which we shall now demonstrate in the blood-vessels of the gland, can alone account to us for those modifications of the properties of the blood.

V. It is very easy to demonstrate experimentally that of the two nerves which we have specified in the submaxillary gland, while the one dilates the vessels, the other constricts them.

The tympano-lingual perve renders the vessels of the gland wider; and this enlargement is such that when the nervous action is intense, the blood passes from the artery into the vein without losing the cardiac impulse, and we then see it spurt from the vein of the gland in jets, just as it does from an artery; then that venous pulsation ceases as soon as the action of the tympano-lingual nerve diminishes or ceases entirely.

The sympathetic nerve, on the contrary, constricts the glandular bloodvessels in a manner very evident. When we excite this nerve, the con

stricted vessels suffer less and less blood to pass. The sanguine fluid, retained in the capillary vessels of the gland, flows feebly through the vein, showing a black color, and the more black in proportion as the sanguine current is the more enfeebled.* When, as sometimes happens, the current of the blood has been entirely arrested by the nervous action, on its ceasing to act we see a current of very black blood escape; then the blood assumes a red color, brighter by degrees, in proportion as the circulation is accelerated, and the blood which had been previously retained in the tissue of the gland is expelled from it.

In this last analysis we see that the two nerves, which modify the color of the venous blood, rendering it red or black, are two motor nerves, which act primarily in constricting or dilating the blood-vessels. The sympathetic is the constrictor of the vessels, the tympano-lingual their dilator.t

VI. In the physiological state of the submaxillary gland, that is to say, in its normal condition of functional action, we must represent its two orders of nerves as being constantly in activity and antagonism of such a nature that the effective nervous action is always due to the nerve actually predominant, and that the special influence of one of the two glandular nerves exerts itself in proportion as it has previously annihilated the action of the other. The proof of this is, that each of the nerves becomes more excitable, and reäcts with greater intensity as a special excitant, when its antagonist nerve has been previously destroyed. This last phenomenon is very decisive, especially in reference to the tympano-lingual nerve. When, for example, this nerve remaining intact, all the glandular filaments of the sympathetic are divided, and a little vinegar has been placed on the tongue, we see the scarlet blood flow through the vein with an intensity much greater, and the venous pulsations much more energetic, than in the normal state of the nervous antagonism; that is to say, when the sympathetic has not been divided. This difference of excitability in the tympano-lingual nerve is the more

* If we compress the vein, or a coagulum exists there, the accidental impediment to the circulation equally produces a black color in the blood. It is important to know these circumstances, in order to guard against all occasions of error in estimating the nervous influences.

† It is not here the proper place to inquire what explanation we may be able to give, in the present state of our knowledge, of the enlargement of the vessels and the increased activity of glandular circulation under nervous influences. I confine my attention for the present to the establishment of the fact which appears to me important, and which is besides established on the strongest evidence.

interesting to establish that we find it measured by its proper physiological excitant, the gustatory impression. All this, then, demonstrates to us in the submaxillary gland the existence of a sort of unstable physiological equilibrium, or of a kind of incessant functional balance, determined by the antagonism of the dilator and constrictor nerve of the capillary bloodvessels. * The extreme dilatation of the capillary system coincides with the direct passage of scarlet and pulsatile blood into the vein; their extreme stricture with the very feeble current of the blood, and with its black color. We can conceive innumerable intermediate conditions between these two extremes, and observation can present them to us in experiments.

VII. To recapitulate. After having successively analyzed all the conditions of that mechanism by which the tympano-lingual and great sympathetic nerves cause the venous blood of the submaxillary gland to appear alternately red and black, we have arrived at this conclusion, that these two nerves do not really act there, except in the way of influencing the constriction or dilatation of the blood-vessels. This action, which differs in no respect from that of the motor nerves in general on the contractile or muscular elements, produces as its results, by an entirely natural series of phenomena, a series of physico-chemical modifications in the blood. When the sympathetic nerve acts as the constrictor of the vessels, the contact between the blood and the elements of the gland is prolonged, the resulting chemical phenomenon consisting in the organic interchange which takes place between the blood and the tissues, has had time to operate, and the venous blood issues very black. When, on the other hand, the tympano-lingual nerve, which dilates the vessels, acts, the passage of the blood through the gland is rendered very rapid; the modifications which constitute venosity, and which result from the contact of the blood with the tissues, are imperfectly accomplished, and the blood issues from the vein of a bright scarlet color, and retaining the appearance of arterial blood. Thus we are always able to seize upon an intermediate transaction between the primitive physiological action of the nerve and the chemical phenomenon which follows,

* We may say in general terms that in the physiological condition the emission of saliva from the gland coincides with activity of the tympano-lingual nerve, and the repose of the same gland with the activity of the great sympathetic. The excitation of both orders of nerves always makes the saliva flow; that of the tympano-lingual nerve alone makes the saliva issue much more fluid, and that of the sympathetic nerve produces an excessively viscid saliva. We observe this phenomenon particularly when, all the nerves of the gland having been cut, we galvanize those portions which are still in connection with the gland.

which modifies mechanically the special circulation of the glandular organ.

Finally, I will add that in virtue of the influence of the two nerves whose physiological office we have detected, the submaxillary gland is really in possession of an individual circulation, which in its variations is independent of the general circulation; and what we here say of the submaxillary gland may doubtless be advanced in behalf of all the organs of the economy. The pressure of the arterial system and the cardiac impulse are the general mechanical conditions which the circulation as a whole dispenses to all the organs. But the special nervous system, which actuates each separate capillary system, and every organic tissue, regulates in every part the course of the blood in accordance with the special functional condition of the organs. These nervous modifications of the capillary circulation take place in every region, without occasioning any perturbation in the circulation of the neighboring organs, and much more without affecting the general circulation. Every part is bound in association with the common conditions of the general circulation, and at the same time, through the intervention of the nervous system, every part can have a proper circulation and physiologically individualize itself.

Such are the special physiological conditions impressed by the nerves upon the capillary circulation, and which it has appeared to me indispensable to establish before entering on the study of the chemical constitution of the various kinds of venous blood. It remains to ascertain positively what is the chemical modification of the blood, which takes its origin in the physiological conditions which we have indicated, so as to give occasion to that alternation of black and red in the color of the glandular venous blood. This will be the subject of a new communication.

Il.-CONTRIBUTIONS TO THE MEDICAL TOPOGRAPHY AND Nosolo

GICAL HISTORY OF BEDFORD COUNTY, TENNESSEE.

By Thomas LIPSCOMBE, M. D., of Shelbyville, Tenn.

The geographical position of Bedford county is between 350 and 36° north latitude, and longitude between 9° and 10°, and partakes of the general character of the middle portion of the State as regards geological formations, the same kind of limestone existing as is found in the neighborhood. of Lexington, Kentucky. The county is nearly square, being some twenty-five miles from east to west, and about the same distance

from north to south, and is well watered. Duck River, a stream of some importance, runs through the county from east to west, and affords sufficient water for manufacturing purposes, and is thickly beset with grist and saw-mills, as well as some other manufacturing establishments. There are also numerous creeks of considerable size traversing the county in different directions, and emptying into Duck River. Many of these creeks afford mill-seats also. Notwithstanding their size and boldness in winter, many of them dry up, so as to cease running, in summer; and this feature, viewed in connection with the fact that their course is through fertile soil abounding in vegetable products, which is frequently inundated during the wet seasons, as well as accumulated in masses in the lowlands they traverse, afford abundant materials for malaria in their vicinity. The same is true of the river, and more especially during the years 1841 and 1842, when there were numerous and excessive rises in Duck River, overflowing large tracts of land contiguous to it, and accumulating large quantities of vegetable material. This was followed by a general prevalence of bilious remittents and intermittents; but along the course of the river particularly, this class of fevers prevailed most in exceedingly dry years, when the river gets lower than it has been for a number of years, thereby exposing to the sun's rays an earthy surface along the margin of the river, that had been protected from direct solar influence for a number of years. The eastern and southern portion of the county is rolling, and even broken, and is most abundantly supplied with springs and running water. The northern and western parts of the county are more flat, and as usual not so well supplied with water, particularly running water, as the southern and eastern portions. The hills above alluded to contain much blue limestone, yet on their surface a considerable amount of silex may be seen. When not too steep for cultivation, they produce nearly or quite as abundantly as the lowlands or valleys; and what appears to me a little strange, vegetation on them does not so soon suffer for lack of rain as in the valleys between them. Fossils of different kinds, and rock, composed mostly of shells petrified, are abundant on many of these hills.

The barren lands of Coffee and Franklin counties join this county on the east and north-east, and constitute a part of the table-lands of the Cumberland mountains. Here the rock is tolerably pure silex, and the waters flowing from this direction beautifully transparent, and but slightly impregnated with lime-indeed, it is generally designated freestone. And yet, but a little distant, the abundant supply of pure limestone at the base of the hills plainly indicates the character of the water flowing from their bases.

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