General Anatomy, Applied to Physiology and Medicine, Vol. 2 (of 3)

by Xavier Bichat

Cellular Texture.

The cellular texture is very abundant in the muscular system; I know of no system that has a greater proportion of it. This texture forms a very evident covering around each muscle. This covering is most commonly loose, filled with fat, easily distended with air in emphysema and serum in anasarca. At other times it is more dense, compact and really arranged like a membrane. Such, for example, is the case with that which covers the great oblique muscle of the abdomen, and the dissection of which on this account, students at first find very difficult. The other abdominal muscles, the trapezius, the serratus major and the great dorsal exhibit also this arrangement. We might say that in this way nature compensated for the aponeuroses, which are wanting on the broad muscles of the trunk. Besides, this covering has only a membranous appearance; it has nothing of its organization, it disappears in the infiltration in which all the true membranes remain.

Besides this general covering of the muscle, each fasciculus has a less covering, each fibre a still less one, and each smaller one a real though almost insensible sheath. We can then represent the cellular texture of the muscles as forming a series of coverings successively decreasing. These coverings favour the motion of the fibres which they separate, either by the serum of the cells, or by the fat they contain, both fluids, by lubricating, allow them to slip more easily upon each other. Frequently between these fibres, the cellular texture appears to form a kind of cross pieces which go at right angles. We see this arrangement especially in the proper extensor of the great toe, and in the common extensor, the fleshy fasciculi of which are broad and delicate when distended. In most of the thick muscles nothing similar is observed.

The quantity of intermuscular cellular texture is remarkably variable. In general, in all the broad muscles and in all the large, long muscles, it is very abundant. It is less in proportion between the fibres of those of the vertebral canals. Back of the neck, the splenii, complexi, &c. have less of it than many others, especially in the spaces that separate them.

Sometimes very considerable cellular elongations are found in the middle of the muscles, and seem to divide them into two; such is that which separates the clavicular portion of the great pectoral; this has even sometimes embarrassed anatomists as to the division of these organs.

The cellular texture in general fixes the muscles in their position; the art of dissection proves it. The effusions of pus which often perform the office of the scalpel, render also very evident this use, which does not prevent the motion in all directions, that the great extensibility of the cellular texture allows. The cellular texture not only fixes the muscles to each other, but it also attaches each of their fibres to neighbouring ones; it flattens them when they contract, and elongates them when they are distended; if they are deprived of it their motions become irregular and uncertain. I have many times separated with a scalpel a muscle laid bare in a living animal, into many small fasciculi; in afterwards making this muscle contract by the irritation of the medulla, by means of a stilet introduced into its canal, I have observed in an evident manner this irregularity of motion. Cut longitudinally a muscle of an extremity from its superior tendon to its inferior, so as to divide it into two or three entirely distinct portions, irritate afterwards one of these portions, the other or the two others will remain almost always at rest, whilst a single irritated fibre in a sound muscle, puts in motion the whole of that muscle. The section of the vessels and the nerves has no doubt a little influence upon this phenomenon; but that of the cellular texture certainly contributes to it also.

In dropsical subjects, the serum of the intermuscular texture is often reddish; this phenomenon is owing to the action of this serum after death upon the colouring substance. I believe that this can take place during life only with great difficulty. The fat sometimes abounds in this texture, to such a degree that the fleshy fibres disappear and the fat only is visible; but oftentimes also the yellow appearance of the muscular fibres, which is produced by the absence of the colouring substance, is taken for this fatty state of the muscles. I have seen the first state but rarely; the second is extremely frequent; we are sometimes deceived at first view. But ebullition and combustion easily prove, that the fat is wholly foreign to this want of colour of the muscles examined in this state.

Blood Vessels.

The arteries of the muscles are very apparent; they come from the neighbouring trunks, penetrate the whole circumference of the organ, more however towards its middle, than towards its extremities. They run at first between the principal fasiculi, then divide and their divisions go between the secondary fasciculi, subdivide and wind between the fibres, and finally become capillaries and accompany the small fibres, in which they deposit by the exhalant system the nutritive matter. There are but few organs, which have, in proportion to their size, more blood than the muscles.

The blood is essentially necessary to support their excitability, as we shall see; it is that which colours the muscular texture, but not, as it at first seems, by circulating in its texture. The circulating or free portion contributes but little to it. It is the portion combined with the muscular texture, that which contributes to its nutrition, that gives it its colour; the following are proofs of it: 1st. The fibres of the intestines are as much or more penetrated with the circulating blood, than those of the muscles of animal life, and yet their texture is evidently whitish, where these vessels are not found. 2d. Many animals with red and cold blood, frogs in particular, have muscles almost white, and yet many red vessels run through this white texture. 3d. I have observed that in animals destroyed by asphyxia, the colouring substance does not change colour, no doubt because it is slowly combined with the muscle by nutrition; that on the contrary, if we cut a muscle of these animals in the last moments of life, whilst the venous blood still circulates in the arterial system, this blood flows out by black jets from the muscular arteries, the muscular texture itself remaining red. This curious experiment, which I have noticed in another work, is made by producing asphyxia in an animal by compressing the trachea, or by intercepting the air in any other way in this tube, whilst we examine the system of the muscles. When a muscle has been exposed for some time to the contact of the air, to that of oxygen especially, its red colour becomes evidently more brilliant.