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

by Xavier Bichat

We should have a very inaccurate idea of the mixture with the blood of the foreign substances brought by the way of the intestines, the skin, or the lungs, for the purposes of sanguification, if we compared it to the mixture of inert substances, or chemical combinations. The blood enjoys, if we may so say, the rudiments of organic sensibility; and as the life which it enjoys places it more or less in relation to the fluids that enter it, it is more or less disposed to combine with them and to endow them with the life with which it is animated. Sometimes it repulses for a long time substances that are foreign to it. I am persuaded that a great number of the phenomena that we experience after taking food, especially acrid substances, and spirituous liquors, arises in part from the general disorder that the blood undergoes when its vitality begins to communicate itself to these foreign substances from the kind of struggle which takes place in the vessels, between the living fluid and that which does not live. Thus we see all the solids rise, as it were, against a stimulant they are unaccustomed to. Who knows but that the vitality of the fluids has an influence upon their motions? I think it is very probable. I doubt whether fluids purely inert could, if they were alone in animated vessels, circulate like living fluids. In the same manner, animated fluids could not move themselves, if they were in vessels deprived of life. Life then is equally necessary to one and the other. But these subjects are too obscure to occupy us longer.

V. Of the properties independent of life.

These are what I call properties of texture. Foreign to inert bodies, inherent in the organs of living bodies, they arise from their texture, from the arrangement of their particles, but not from the life that animates them. Thus death does not destroy them. They remain in the organs when life is gone; that, however, adds much to their energy. Putrefaction and the decomposition of the organs, alone destroy them. The two first of these properties are extensibility and contractility of texture. I have explained these sufficiently in my Treatise on Life. I shall have occasion in this work to explain the influence they have in each system. I shall now speak of a property of which as yet very little has been said; which chemists have proved by their experiments, and which physiologists have confounded often with irritability, but which is as distinct from it as it is from the contractility of texture; I mean the property of being[3] hardened like horn, and contracted by the action of different agents. This will be examined particularly in each system; I shall now describe it in a general manner only.

Every organized part, submitted either after death or during life, to the action of fire and of certain concentrated acids, is contracted and wrinkled in different ways, and is affected almost like irritable organs when they are excited. Now this property is to be considered as to the agents which put it in action, as to the organs which are the seat of it, and as to its phenomena.

1st. Fire is the principal agent of this horny hardening. Every living organ, placed upon burning coals, is suddenly raised to the highest degree. 2d. Next to fire, the strongest acids, the sulphuric first, then the nitric, then the muriatic, make the animal fibres contract most suddenly. As they are diluted, they lose this power, and the acids that are naturally very weak have hardly any of it. 3d. Alkohol is much less powerful in producing this effect, though it may be highly concentrated. It contracts, however, the texture of parts, which it condenses and even twists. So that those who preserve anatomical specimens, find it necessary to dilute the alkohol. 4th. The neutral salts, after being moistened by the humidity of animal substances, condense and harden them wonderfully after the lapse of a considerable length of time. 5th. When the air has taken away, by drying, the aqueous particles of the solids, these continuing exposed to its action, contract, wrinkle, and twist in a slow and gradual manner. 6th. The alkalies, however strong they may be employed, do not produce any kind of horny hardening. 7th. Water appears to act in a manner opposite to this horny hardening; it dilates, spreads the organs by maceration, and separates their particles. It is when it is combined with much caloric that it produces horny hardening. This phenomenon takes place at some degrees below boiling, and is very remarkable at that point.

The different agents of which I have just spoken, produce, then, two species of horny hardening: 1st. the first is prompt, sudden, almost like the motion which results from the irritation of a living muscle: 2d. the other slow, gradual, and even insensible. Fire and the strong acids are in a special manner the agents of the first. The action of the neutral salts, of the air, of alkohol, principally produce the second.

These two species differ very much in their results. The state to which the first reduces the organ, is soon changed if the hardening cause continues. 1st. Fire continuing to act upon the solids, reduces them to a hard and coaly mass. 2d. Boiling water, after a length of time, destroys by degrees the hardness the solids had suddenly acquired, by being plunged into it. As the hardness diminishes, the effect of the boiling increases, and it arrives at the greatest extent, when the solid, having lost all consistence, becomes pulpy. 3d. Animal organs that have been acted upon suddenly by the acids, and become consequently hard, soon grow soft and change into a true pulp. This double phenomenon, that is presented on the one hand by boiling, and on the other by the strong acids, has a great analogy, and seems to be derived from the same principle.

The slow and insensible horny hardening, the effect of the contact of neutral salts, such as alum, the muriate of soda, &c. of the air and of alkohol, offers a very different phenomenon from the first. It is not altered by the continued action of the cause that produced it, however long it may be; it does not soften in a slow and insensible manner, as it has hardened, but remains always firm and contracted.

Are these two species only different degrees of the same, or are they derived from separate principles? I know not. I have only observed, that when the living solids have undergone the slow and gradual horny hardening, they are still susceptible of the other. We know that after many years drying, animal textures are hardened, as in a recent state, by the action of fire; I have made the same observation with regard to boiling and the acids. Textures that have been contracted for a long time by alkohol and the neutral salts present the same phenomenon.

All animal textures are susceptible of sudden hardening, except the hair, the epidermis, and the nails; these, if we may so say, exhibit only the rudiments of it. In general the hardening is more sensible, in proportion as the fibrous texture predominates in the organs. Hence the muscles, the tendons, and nerves, are the most susceptible of it. The organs not fibrous, as the glands, show the least degree of it. The slow and insensible horny hardening is almost the same in every part. Both exist in textures deprived of animal contractility, of sensible organic contractility, and of contractility of texture, as well as in those which enjoy them in the highest degree. Thus the tendons, the aponeuroses, the bones, even when their calcareous substance has been removed by acids, may be hardened as well as the muscles and the skin. This single circumstance would suffice to distinguish the contractility arising from hardening from all others, if a variety of differences, which I shall point out hereafter, under the article of the muscles in particular, did not.