Physiological Researches on Life and Death

by Xavier Bichat

They both succeed each other, and are connected in the same way, as in the vital phenomena, the organic and animal sensibilities are related to their respective contractilities.

Extensibility of texture, or the faculty of being distended beyond the ordinary state by external impulse (and in this it is distinguished from the extensibility of the iris,[35] the corpora cavernosa, &c.) This extensibility, I say, belongs to many organs. The extensor muscles are very much lengthened in strong tension of the limbs; the skin accommodates itself to tumours; the aponeuroses, as we see in ascites and pregnancy, are distended by what is accumulated beneath them. The mucous membranes of the intestines, of the bladder; the serous membranes of the greater number of the cavities present us with similar phenomena, when these cavities are full. The fibrous membranes, the bones themselves are susceptible of distension. Thus in hydrocephalus the pericranium, and the bones of the cranium, in spina ventosa and other analogous diseases, the extremities or the middle of the long bones experience a similar distension. The kidneys, the brain, and the liver, when abscesses are formed in their interior, the spleen and the lungs, when penetrated by a great quantity of blood, the ligaments in articular dropsies, in short all the organs, under a thousand different circumstances, exemplify this property; a property inherent in their texture, and not precisely depending on their life; for as long as their texture remains untouched, their extensibility subsists also, though they themselves have ceased to live.—The decomposition of the part, from whatever cause it happens, is the sole term of this extensibility, in which the organs are passive at all times, and subject to the mechanical influence of those bodies which act upon them.

There exists for the different organs a scale of extensibility, at the top of which are those which have the greatest laxity in the arrangement of their fibres, as the muscles, the skin, and cellular substance; at the bottom of the scale are those which are characterized by their density, as the bones, the cartilages, the tendons, and the nails.

We must not, however, be deceived by appearances, with regard to the extensibility of parts of the body; for the serous membranes, which at the first glance would seem to be capable of great distension, do not yield so much of themselves, as from the development of their folds. Thus the displacement of the skin, which abandons certain parts, while it spreads over tumours in the vicinity, might easily give rise to the supposition of its being capable of a much greater distension than that of which it is really susceptible.

With extensibility of texture, there corresponds a certain mode of contractility, which may be designated by the name of contractility of texture. This can only take place after a previous distension.

In general the greater number of our organs are maintained in a certain degree of tension from different causes; the locomotive muscles by their antagonists, the hollow muscles by the different substances which they enclose; the vessels by the fluids, which circulate within them, the skin of a part by that of the neighbouring parts, the alveolar parietes by the teeth which they contain. If these causes be removed, contraction supervenes; thus, if a long muscle be cut, its antagonist will be shortened; if a hollow muscle be emptied, it will contract; if an artery be deprived of its blood, it will become a ligament; if the skin be cut into, the borders of the incision will retire from each other; if a tooth be drawn, its cavity will be obliterated.

In these cases it is the cessation of the natural extension, which occasions the contraction; in other cases it is the cessation of an unnatural extension which does so. Thus, the lower belly is straitened after puncture or delivery; the maxillary sinus, after the extirpation of a fungus; the cellular texture, after the opening of an abscess, the tunica vaginalis, after the operation of hydrocele, the skin of the scrotum, after the extirpation of the voluminous testicle, by which it was distended; the sac of an aneurism, after the evacuation of the fluid.

This mode of contractility is not by any means dependent on life; it belongs only to the texture, to the organic arrangement of the part,[36] yet still receives from the vital powers an increase of energy. Thus the retraction of a muscle, which is cut in the dead subject, is much smaller than that of a muscle divided in the living animal; in the same way, the retraction of the skin varies; but though less evident, this contractility subsists always, and like its corresponding extensibility has no other limit than that of the decomposition of the part.

The greater number of authors have confounded the phenomena of this contractility with those of the insensible organic contractility, or tonicity. Of these I might reckon Haller, Blumenbach, Barthez and others, who have referred to the same principle the return upon themselves of the abdominal parietes, after distension, the retraction of the skin, or a divided muscle, and the contraction of the dartos from cold. The first of these phenomena is owing to the contractility depending on texture, which does not suppose the application of an irritating substance; the second, to tonicity, which is never exercised excepting when influenced by such application.