By Deane Juhan
A transparent fluid ground substance is found to one degree or another in all of the body's connective tissues, and it may be thought of as the basis for the production of all their other forms. This viscous liquid, much like raw egg whites in appearance and consistency, surrounds all the cells in the body, and is a part of the internal ocean.
However, it is quite distinct in its origins and its functions from the other intercellular fluids which seep from capillaries or from other tissue cells. These latter fluids are mostly plasma, nutrients, and hormones diffusing from the blood vessels to the cell, and metabolic wastes from cell activity diffusing back to the capillaries and the lymph vessels. The ground substance of connective tissue is different from all of these fluids; it is the liquid medium through which these other fluid exchanges take place. It is the retort in which all extracellular activities occur. It does not come from the capillaries or from other tissues, but is produced by cells which are among the earliest specialized cells to emerge from the embryonic mesoderm, the fibroblasts.
Technically, we must speak of ground substances in the plural, because even the make-up of this basic fluid varies from location to location. Essentially all these varieties consist of a carbohydrate combined with a protein chain-a mucopolysaccharide-but the chemical variations are complex, and they account for many different properties found in the ground substance in different locations. Some of the mucopolysaccharides are large and dense, creating a ground substance with a more viscid gel-state, while others are smaller molecular units which create a more fluid sol-state. And these compounds themselves are not inert, but are constantly changing their arrangements in healthy, active tissue.

These fluid ground substances are the immediate environment of every cell in the body, and they undoubtedly have a wide range of effects upon every cellular membrane which they contact. Their chemical activities are legion, and so they also directly influence the passage of all sorts of gases, nutrients, wastes, hormones, antibodies, and white blood cells between the capillaries and the tissues they irrigate.

We can regard these ground substances as both facilitators and as barriers between the blood and all the cellular surfaces, chemical filters which regulate many interactions. Damage to their elements through malnutrition, trauma, fatigue, stress, and the like results in the impairment of these supporting functions or by altering the chemical properties of the mucopolysaccharides. Such disruption strikes at the very basis of healthy metabolic activity. Healthy ground substance works constantly to help maintain a supportive chemical and physical equilibrium between all the body's tissues.
The Collagen Fibers
Although this ground substance forms the fluid medium for the ongoing activity of connective tissue, the most abundant constituents of this intercellular support system are the long white fibers of collagen. As we have noted, these fibers account for more than one third of all animal protein. They are the chief fibrous content of skin, ligaments, tendon, cartilage, bone, vessels, and all organs, and their tough strands give to these tissues their shape, their tensile strength, their resiliency, and their structural integrity. These fibers can be arranged in any number of ways to produce a wide variety of properties; they may be crisscrossed randomly in blocks or sheets, carefully stacked in alternating layers like plywood, spun into loose areolar webs, or packed into dense parallel formations.

These fibers are not living tissue, but are made up of protein chains that are produced by the same living cells which exude the fluid ground substance, the fibroblasts. In the embryo, these fibroblasts develop in the mesenchyme, from which they are dispatched throughout the growing organism. When they settle in a particular area, they begin manufacturing and secreting collagen chains, which then respond to local chemical properties and specific stresses in the area to form the appropriate kind of fibers and arrangements-sacs around the muscles, ligaments across the joints, the walls of blood vessels, the cornea of the eye, and so on.

Of all the cells in the body, these fibroblasts are the only ones which retain throughout our lives the unique property of being able to migrate to any point in the body, adjust their internal chemistry in response to local condition, and begin manufacturing specific forms of structural tissue that are appropriate to that area. No other cell exhibits this wide rage of regenerative activity, and this makes the fibroblasts the key element in wound healing of all kinds; scar tissue is new collagen that has been secreted by fibroblasts which have migrated to the injury.
Fluid Crystal
We have already seen that the ground substance can vary considerably from a watery sol-state to a viscous gel-state. Now this variable fluid base may be combined with varying proportions of collagen fibers to produce a truly remarkable array of different properties and structural functions that can be observed in different kinds of connective tissues. Where we find mostly fluid and few fibers, we have a watery intercellular medium that is ideal for metabolic activities; with less fluid and more fibers, we have a soft, flexible lattice that can hold skin cells or liver cells or nerve cells into place; with little fluid and many fibers, we have the tough, stringy material of muscle sacs, tendons, and ligaments. If chondroblasts (cartilage-producing cells) and their hyaline secretions are added to this matrix, we obtain even more solidity, and in the bones this cartilaginous secretion is replaced by mineral salts to achieve a rock-like hardness.

Taken as a whole, the, connective tissue in its various forms can be regarded as a fluid crystal, a largely non-living material that can be adjusted over a wide range from sol to gel-here watery, there gelatinous, here dense and elastic, there hard as a stone. In the growing animal, this liquid crystal is in its most active state, changing from sol to gel and gel back to sol with great facility, as rapid growth demands.

Organ shapes are outlined by genetic codes and then continually modified by the specific stresses and strains experienced by the developing organism. Flaccidity, flexibility, and rigidity emerge as the conditions of the life demand. This sol-gel activity should continue, albeit at a slower rate, throughout the adult life of the animal. It accounts for a great deal of our metabolic efficiency, is responsible for the healing of all injuries, and provides the physical adjustments necessary for new muscular bulk, new habits, new skills.

However, there are some limiting factors in these fluctuations, factors which tend to become even more problematical as our tissues age and our varieties of physical activities decrease. First of all, connective tissue shares with many other gels a phenomenon called thixotropy: It becomes more fluid when it is stirred up, and more solid when it sits without being disturbed. This is exactly the case with common gelatin, which solidifies while sitting in the refrigerator and melts when it is whipped vigorously, or when it is exposed to low hear.

In the human body the heat energy and movement required for appropriately solvent states of connective tissue can be provided by rapid and efficient metabolism (a chemical "burning), by physical work, aerobic exercise, stretching, and the like. Unfortunately, these are the very things which we gradual begin to avoid as we get older, less spry, more sedentary. With disuse, the connective tissues become a little colder, less energized, and the thixotropic reaction makes them gel more, become sluggish, lose their full, juicy quality and their ability to soften, stretch, and flex.

There is no way that we know to prevent the eventual drying and stiffening of the connective tissues, a process which eventually produces the wrinkled skin and cranky joints of old age. Connective tissue does seem to have some final limits upon its ability to regenerate and maintain its resilient properties, limits which make us the mortal creatures that we are. But there can be no doubt that poor nutrition and sedentary habits weakening all the connective tissues of the body, stiffen them, and can significantly accelerate their biological aging, even in a young adult.
Thixotropy and Bodywork
This thixotropic effect provides one of the cornerstones for effective bodywork. Since connective tissue is largely non-living, it is the mechanical motion and friction caused by muscular activity which provides much of the energy and warmth that maintains its fluid qualities. When a part of the body loses some degree of movement and vitality through trauma or disuse, it will not be as inviting, as comfortable, perhaps not even as possible to move that part with the vigor it requires to keep the connective tissue warm, moist, and resilient. At this point, manipulation of the tissues by the skilled hands can provide a pleasant and extremely effective means of introducing freer movement and higher levels of energy into the connective framework. The hands of the therapist can literally supply the mechanical activity which a sluggish limb fails to produce, raising the metabolic rate and restoring some of the fluidity of its connective tissues.

R.B. Taylor, an osteopathic physician, has stated that, "Manipulative pressure and stretching are the most effective ways of modifying the energy potentials of abnormal tissues." Note well the principle involved here: Nothing chemical or structural has been either added to or subtracted from the connective tissue. Rather, by means of pressure and stretching, and the friction they generate, the temperature and therefore the energy level of the tissue has merely been raised slightly. This added energy in turn promotes a more fluid ground substance which is more sol and ductile, and in which nutrients and cellular wastes can conduct their exchanges more efficiently. In addition to this mechanical stimulation of pressure and stretching, a powerful thermodynamic effect can be produced upon the bioenergetic field of the patient by the stronger and healthier bioenergetic field of the therapist. This comes partly in the form of literal body heat transferred by the therapist's penetrating touch, and partly from subtler forms of energy such as galvanic skin responses or vibratory rhythms.

Thus, with regard to its effects upon the connective tissues, bodywork accomplishes its end in an utterly different fashion than do the additive and subtractive means of pharmaceuticals and surgery. Skillful manipulation simply raises energy levels and creates a greater degree of sol (fluidity) in organic systems that are already there, but are behaving sluggishly. The effect can be analogous to that of turning up the temperature and humidity in a greenhouse that has been too dry and cold.