General Anatomy, Applied to Physiology and Medicine, Vol. 1 (of 3)

by Xavier Bichat

General uses of the circulation of the red blood.

It is the circulation of the red blood that alone furnishes the matter of secretions, except that of the bile, a fluid which however deserves a further examination. It is from this circulation that the serous, cellular, cutaneous, medullary exhalants, &c. draw the fluids that they transmit upon their respective surfaces. All the vessels that carry the matter of nutrition of the organs are also continuous with the arteries and consequently their fluids come from the red blood. In the organs even in which the black blood goes, as in the lungs and the liver, there are vessels with red blood evidently for the purposes of nutrition. It is the red blood that communicates to the organs of the whole body that general agitation which is necessary to their functions, an agitation so evident in the brain. The circulation of red blood is then the most important; it is that, whence are derived the great phenomena of the economy.

General uses of the circulation of black blood.

The circulation of the black blood, on the contrary, having no connexion with any of the functions, seems only destined to repair, if we may so say, the losses the blood has sustained in the preceding one. Observe in fact that a considerable part of the red blood is expended in the exhalations, secretions and nutrition. The principles it borrowed in the lungs and which gave it a vermilion colour, have been left in the general capillary system. It is necessary that the black blood should receive what the other has lost; now a variety of substances enters the great canal that contains it. These substances are internal or external. 1st. The great trunks of the absorbents constantly pour in the lymph of the cellular texture and of the serous surfaces, the residue of the nutrition of all the organs, the super-abundant fat, synovia and marrow. All that which is to be thrown from within out, is first poured into the black blood. 2d. All that which enters in from without, is also received by it. The chyle, the product of digestion, is at first uniformly carried into the general canal, in which it circulates. In the second place, it is with it that are mixed the substances of the air, which pass through the lungs in the act of respiration. In fine, when cutaneous or mucous absorptions take place, the black blood is always the first that receives the product of them.

It follows from this, that the circulation of black blood is, if we may so say, a general reservoir in which is poured in the first place all that is to go out of the body, and all that is to enter it.

In this last respect, it performs an essential part in diseases; in fact it is undeniable, 1st. that deleterious substances maybe introduced with the chyle into the economy, and produce ravages there more or less evident in circulating with our fluids. For this, it is sufficient that the organic sensibility of the chylous vessels should be changed; then they admit what before they rejected, as the glands by changes in their organic sensibility, often secrete fluids that are usually foreign to them. 2d. We shall prove in the article upon the cutaneous system, that it is oftentimes the seat of the absorption of deleterious substances. 3d. We cannot doubt that besides the principles that colour the blood, there often passes through the lungs deleterious miasmata which produce diseases, as my experiments upon asphyxia have proved. The intestines, the lungs and the skin are then a triple gate open, in many cases, to different morbific causes; now these causes that enter thus into the economy are all received in the first place in the black blood; it is not until afterwards that they pass into the red blood.

An evident proof of this assertion is this, that we produce phenomena exactly analogous to those which result from them, by pouring artificially into the black blood those substances that are introduced in a natural way. Thus when a purgative or emetic infusion is introduced into the veins, alvine evacuations or vomiting ensue, precisely as when the substances of these infusions are introduced by friction upon the skin. The experiments of many physiologists leave no doubt upon this point. I am convinced that it is possible to give to animals artificial diseases, by making different substances infused into their veins circulate with the blood. I shall speak of these attempts in the article upon the glandular system. It is sufficient for me to mention them here, in order to prove that the black blood is a general reservoir in which many substances can enter, either naturally, or accidentally, and afterwards disturb the functions by passing into the whole circulating mass. The humoral pathology has undoubtedly been exaggerated, but it has still real foundations, and in many cases we cannot deny, but that every thing arises from the disorders of the humours.

Let us conclude from all that has hitherto been said, 1st. that the essential part which the circulation of the black blood performs in the economy, is to introduce into this blood different new substances; 2d. that that of the system of red blood is to expend on the contrary, the principles that constitute it. One is constantly increasing, the other diminishing; to give is the attribute of one, to receive is that of the other. This sketch, which is perfectly true, and founded upon the most simple observation, appears to me very proper to establish an evident demarcation between the two divisions that I have adopted for the general circulation.

Health supposes a perfect equilibrium between the losses the red blood experiences, and the acquisitions the black blood makes. Whenever this equilibrium is destroyed, there is disease. If the black blood receives more than the red blood expends, plethora follows. That which is called the poverty of the humours, is manifest when more substances go from the red blood than enter the black.

These are I think sufficient characteristic attributes of the two great divisions of the general circulation, to justify the point of view different from other authors, in which I present this important function of the animal economy.