Note 116 — I. Does the Heart cease to act immediately in consequence of the interruption of the cerebral action?

It is shewn by the beautiful experiments of M. Legallois, that the heart derives the principle of its forces from the spinal marrow, and from the whole spinal marrow, since the destruction of one of its three portions can arrest completely the circulation. The destruction of the spinal marrow does not entirely annihilate the motions of the heart; but it weakens them sufficiently to prevent the circulation, and this weakening is so much the greater, as the portion of spinal marrow destroyed is larger. It may be presumed from this, that notwithstanding the weakening which follows the removal of a part of this marrow, the circulation may still continue if we lessen the sum of the forces which the heart must expend to maintain it. For this it is only necessary to diminish by ligatures on the arteries, the extent of the circle to which the heart distributes the blood. This conjecture is confirmed by experiment. It has been seen, for example, that the destruction of the marrow which is very suddenly fatal in full grown rabbits, ceases to be so, if before doing it the abdominal aorta is tied between the coeliac and the superior mesentric arteries. The application of the same principle to other parts of the body leads to a still more surprising result, it is this, that in order to support life in rabbits of a certain age, after having destroyed the cervical marrow, it is necessary first to cut off the head. They will be completely dead if the marrow be destroyed before they are decapitated; this arises from the fact, that by cutting off the head all this part is taken out of the domain of the circulation, and that by it the heart having need of less force to continue its function, we can weaken it by the destruction of the cervical marrow without its ceasing to perform it.