Physiological Researches on Life and Death

by Xavier Bichat

When we adapt to the pipe a bladder full of pure oxygen, the blood is very long in becoming black, but does not at first assume a redder tint than it usually has.

II. The blood which has been blackened in consequence of the interruption of the chemical functions of the lungs penetrates into the organs, and circulates for some time in the vascular system of the red blood.

We have just established what are the phenomena of the alteration of colour in the blood, when the chemical functions of the lungs are suspended. Before we consider the influence of this change upon the death of the organs, let us prove, that they are really penetrated by the blood when so altered.

I have proved it to be a fact, that the force of the heart subsists for some time, notwithstanding the influx of the black blood into it, and have shewn that the black blood is thrown out with a jet, similar to that of the red blood, &c. &c. Hence I might already conclude, 1st, That the arterial circulation continues for a certain time, though the arteries contain a fluid, to which they are not accustomed, and 2dly, That the necessary consequence of such circulation, must be the injection of the different parts of the body with black blood; but we shall deduce the latter conclusion from precise and rigorous experiments. To be certain of this important fact, we have only to expose successively the different organs, while the animal is suffering a death of asphyxia. I have in this way examined the muscles, the nerves, the membranes and the viscera. The following are the results of my observations.

1st. The colouring matter of the muscles, exists in the body in two states—at liberty, or in a state of combination; in the vessels, where it circulates with the blood, or in the fibres, with which it is combined. It forms especially the colour of the muscles, and in such state undergoes no alteration from asphyxia; in its free state it is blackened. The divided muscles furnish an infinity of black drops, which are no other than indices of the divided vessels. Such drops contrast with the red of the muscles; but when circulating within them, are the cause of that livid tint which they then present.

2dly. The nerves are habitually penetrated by a number of small arteries, which creep along within their tissue, and carry to them both excitement and life. In the state of asphyxia the black blood by which they are traversed, is announced by the dull brown, which succeeds to the rosy-white, which is natural to them.

3dly. There are few parts, where the influx of the black blood is more visible, than in the skin; the livid spots so frequent in asphyxia, are only the effect of the obstacles which it meets with, in its passage towards the general capillary system, to the organic contractility of which it is not a sufficient excitant. To this cause also is owing the tumefaction of certain parts, such as the cheeks and lips. This phenomenon we have seen already in the lungs, they cannot be traversed by the blood and therefore become in the last moments of life, the seat of a fulness, which affects the whole of the capillary system there; but for the reasons, which I have assigned, such fulness is always more evident in the capillary system of the lungs, than in that of the system in general.

4thly. The mucous membranes also, when the chemical functions of the lungs are interrupted, exemplify a similar phenomenon. The swelling of the tongue, observable in those that have been drowned or hanged, or asphyxiated by the vapour of charcoal, the lividity of the membrane of the mouth, of the intestines, and the bronchiæ which have also been remarked, depend on no other cause. The following is a proof of this assertion:

Drag out of an animal a portion of the alimentary canal and divide it in such way as to expose its inner surface. Then shut up the pipe which has been previously adapted to the trachea, and at the end of four or five minutes, a brown tint will succeed to the red one, which is natural to this surface.

5thly. I have made the same remark upon the fleshy granulations of a wound, inflicted on an animal, for the purpose of observing the manner in which they are coloured by the black blood. In the two last experiments, this phenomenon is slower in taking place than in many other circumstances.