« SebelumnyaLanjutkan »
I. ON THE INFLUENCE OF THE TWO ORDERS OF NERVES IN
DETERMINING THE COLOR OF VENOUS BLOOD FROM THE GLAN-
By M. CLAUDE BERNARD.
(Translated for the Nashville Monthly Record by DANIEL F. WRIGHT, M. D.)
[The following lecture by M. Bernard will be interesting to all lovers of physiological science. It must be considered as a continuation of the line of research adopted by him in the lectures prepared for the summer session of the College of France, A. D. 1856, in which his experiments had reference to the various glands emptying into the alimentary canal, but especially the salivary and pancreatic glands. Some of the subjects treated of in his lectures on the blood, delivered in the winter of 1853– 4, are also here resumed. It will be seen that another lecture on the chemical conditions which determine the changes in color of the venous blood from the glands was to follow the present. This is already received, and will appear in our next number; after which we hope to
* From the Proceedings of the Academy of Sciences, sitting of August 9, 1858. M. Despretz, President.
present some remarks of our own regarding the influence of the nerves on secretion, nutrition, etc. Our January number will also contain a cut of M. Bernard's dissections, illustrating the nervous relations of the submaxillary gland with the lingual and facial nerves, and the superior cervical ganglion of the sympathetic.-D. F. W.]
In a communication made at the sitting of January, 25th ultimo, I showed that the venous glandular blood and the venous muscular blood presented phenomena of coloration diametrically opposite when examined during the activity of the respective organs.
When a muscle is active, and contracts, the venous blood which proceeds from it is very black. When a gland is in function, and discharging the products of its secretion, the venous blood which it affords is, on the contrary, of a bright scarlet color, exactly identical with that which the blood of the arteries exhibits; whence it follows, that in the glands whose secretion is intermittent, there is an alternation of red and black coloring in their venous blood, according as the organ is in the one or the other of those two physiological conditions which have been denominated the state of function and the state of repose.
After having established these original facts, I pursued my researches, with the object of determining what are the modifications of composition which correspond with such marked differences in color. I have succeeded, I believe, in discovering that explanation. But before entering on the exposition of the experiments which are directed to the purely chemical aspect of the question, I think it indispensable to explain the physiological conditions of the nervous system which regulate these special chemico-organic actions. I shall lay special stress on this subject, because the study of that mechanism of the nerves by which they influence the chemical phenomena which take place in the living organism has always appeared to me the capital object with which the physiologist ought to occupy himself. .
I. I desire to show to-day that the special chemical conditions which, in the glands, make the venous blood appear alternately red and black, are determined by the influence of the two nerves, which have distinct origins, and possess an action in some degree antagonistic. Or I might express it in other terms, that there exists a glandular nerve, which permits the venous blood to flow on red, and another, which causes it to come forth black. I shall next demonstrate that each of those nerves, for the purpose of acting chemically upon the blood, modifies in an opposite manner the mechanical conditions of the capillary circulation which are under the immediate influence of the nerves.
For the purpose of rendering our facts more definite, and of facilitating the researches of those who may desire to reproduce them, I ought to say that all the results of experiments which we are about to consider have been obtained from the submaxillary gland of the dog, which is peculiarly adapted to researches of this class by the intermittent character of its secretion, which renders very plain the variations in the coloring of its venous blood.
The mode of operation convenient to follow for the purpose of exposing the nerves of the submaxillary gland need not now be described, as this is a process of vivisection which every physiologist can execute in his own manner. I will only say that this experiment, which should be classed
among the more delicate and laborious operations, will be much simplified if, as I have always practiced it, the digastric muscle be first entirely removed. After its removal, which ought to be effected by a careful dissection, without wounding the adjacent organs, we obtain an excavated wound, in which is seen the deep surface of the submaxillary gland, together with all its vascular and nervous apparatus, upon which it will then be quite easy to make our experiments.
II. The nerve which makes the venous blood in the rein of the submaxillary nerve appear red, is a twig which comes off from the fifth pair behind its lingual branch; but it does not really belong to the fifth pair : it proceeds really from the seventh, and is chiefly supplied with fibres from the chorda tympani: at any rate, that glandular nervous filament may be easily reached where it detaches itself from the lingual nerve to be distributed in the submaxillary gland in company with its excretory duct.
Now, when we observe the submaxillary gland, provided with all its nerves, in the state of repose-—that is to say, when nothing is passing along its excretory canal—it is evident that its venous blood possesses a decidedly black color; but if at that moment we excite the secretory function of the glandular nerve specified above, we see the venous blood, which previously flowed black, come forth more and more red, and very soon of the true arterial hue, provided the nervous action has been sufficiently intense. This fact is constant, and permits us to establish as a physiological proposition, that so long as the action of this tympano-lingual nerve expresses itself with energy, the venous blood of the submaxillary gland appears scarlet, while it appears black whenever that nervous twig ceases to act, or its action ceases to be preponderant.
Nothing is easier than to give an experimental proof of this special influence of the tympano-lingual nerve on the red color of the venous blood. In fact, after having exposed the glandular vein and the nervous twig
in question, we make a gustatory impression on the tongue by pouring a little vinegar into the mouth, we see the blood rapidly become scarlet in the vein, because the gustatory impression produced on the tongue, and conveyed to the nervous centre, has been transmitted by reflex action through the chorda tympani. The truth of this interpretation presents itself immediately; for if we cut this tympano-lingual nerve at the spot where it separates from the lingual, we see that the venous blood of the nerve remains black; and from that moment, in spite of the introduction of vinegar into the mouth, in spite of the sensation of taste being excited, the scarlet color of the blood no longer reäppears, because the nervous tract by which that influence, modifying the condition of the blood, should arrive, is cut off. But, on the other hand, if, taking this glandular nerve at the point where one has made the section behind the lingual nerve, we irritate by means of galvanism its peripheral portion, still in communication with the gland, we immediately see, under the influence of that artificial excitation, the blood flow from the gland into its vein of the same scarlet color, and then become black again as soon as the excitation ceases.
This last experiment, then, furnishes a new argument to prove that the red color of the venous blood of the submaxillary nerve is associated with the activity of the tympano-lingual nerve, and its black color with the quiescence of that nerve. But we must not suppose that, during the repose of the gland, the black color observed in its venous blood is no more than a passive result of the paralysis or default of action of the tympano-lingual nerve. That black color is itself due to the active state of another nerve, which is employed in rendering the blood black, and the permanent influence of which exhibits itself as antagonistic to the tympano-lingual nerve, whose function seems to be specially characterized by an intermittent action.
III. The nerve which renders the venous blood black in the submaxillary gland proceeds from the great sympathetic, and arrives at the gland in company with the arterial branches of the external carotid, which supply it with blood, the one, smaller, entering the gland on its superior and posterior aspect, the other, its principal angular artery, entering the hilus of the gland at the same passage with its excretory duct. These sympathetic nerve - fibres, for the most part, come off from the superior cervical ganglion, besides which they anastomose with fibres proceeding from other sources, and especially with the mylo- hyoid branch at that point where the nerve crosses the direction of the facial artery.
So long as we contemplate the submaxillary gland with all its nerves
in a physiological condition and at rest, its venous blood, as we have said, is black. Now this depends upon the fact that at that moment the activity of the great sympathetic, which renders the blood black, is predominant over that of the tympano-lingual nerve, which renders it red. This is very easily proved; for, in that condition, if we cut those sympathetic branches which are distributed to the submaxillary gland, we see the venous blood lose its black color to assume a scarlet hue, which becomes permanent, because the nervous influence of the sympathetic is intercepted before it arrives at that gland. But if, on the other hand, we artificially establish the activity of that nerve, and if we excite by galvanism the peripheral portion of its filaments, it presently appears that the blood issues from the gland very black, and recovers its red color as soon as the galvanism of the nerve ceases to act. We are enabled, then, to state a proposition in reference to the sympathetic nerve the reverse of that which we expressed in relation to the tympano-lingual, and to say that the venous blood of the submaxillary gland is black so long as the sympathetic nerve is in action, and that the intensity of its blackness is proportional to the energy with which that nerve is acting.*
From what has been said, then, we have gained the experimental demonstration of the fact that the variations in the colors of the glandular venous blood are due to two determinate and perfectly distinct nervous influences; but how are we to comprehend the mechanism of that nervous influence upon the blood? There is no anatomical continuity, and, in consequence, no direct chemical action possible on the part of the nerves upon the globules of the blood, such as to modify their color. Other intermediate phenomena must therefore intervene between the nervous action and the chemical modification of the blood-globule. In fact, these intermediate conditions exist, and are determined by the various mechanical modifications which the respective nerves exercise upon the capillary circulation of the gland-modifications which we shall now examine.
IV. The mechanical conditions of the capillary circulation, which are
* The glandular nerves present along their course various anastomoses with the sensitive nerves, which give them a sort of recurrent sensibility. There are, besides, ganglia, which exercise an influence upon the results of the experiment, whether we make the section above or below the ganglion. Without wishing to introduce the study of these ganglionic influences into a subject already so complicated, I will mention that, to obtain the results which I am reporting, I have always divided the sympathetic fibres between the nervous ganglia and the submaxillary gland.