We must not judge of the vessels of the cellular texture by injections. When they are fine and have succeeded well, a thousand different threads interlaced in every way, destroy its whitish colour and change it into a vascular net-work. The appearance of a body thus injected is deceptive; it arises from this, that the exhalants have admitted a fluid forced through the arteries, whilst their own sensibility would repulse the blood in an ordinary state. In dissecting the cellular texture upon a living animal, it is seen to be white as in the dead body, and that great trunks that do not belong to it, send off in passing through it different branches and ramifications that are evidently lost in it. In raising the skin from the subjacent organs, the sub-cutaneous texture is distended, and we may clearly distinguish in it different little branches that end there; this is remarkable in dogs. By first making the cellular texture emphysematous, the experiment succeeds better. We see, also, very well in this way, that the blood varies in the vessels; often after being exposed sometime to the air, there appears double the number of them there was when it was laid bare. There are always remarkable variations, if the place that is denuded is examined even for a short time; it is the blood retained in the exhalants, and it seems thus to increase the number of little arteries.
Exhalants.
The existence of the exhalants is rendered evident, 1st. by the preceding experiment, which is a natural manner of injecting them; 2d. by artificial injections, which shows there many more vessels than ordinary; 3d. by transudations that sometimes take place in the cells, when these injections are driven with much force, transudations that really form an artificial exhalation; 4th. by natural exhalation, which is continually going on, and which has for its materials the fat and the serum; 5th. by accidental exhalations that sometimes take place, as when the blood is diffused in and colours serous infiltrations, &c.
Few systems in the living economy are furnished with a greater number of exhalants; I do not speak of those that contribute to its nutrition and that are consequently found there as in all other organs. The superabundance of these vessels is owing to the continual exhalation that is going on there. It is this superabundance which renders, as we shall see, inflammation so much more frequent in a part where the cellular texture is in the greatest abundance; it is this that exposes it to that variety of alterations, in which its texture, loaded with the different substances it exhales, has a firm appearance, and offers at one time a fatty substance, at another a gelatinous one, sometimes a species of scirrhus, &c. &c.
Absorbents.
The absorbents correspond with the exhalants in the cellular system; the eye cannot trace them, injections would not reach them. But their existence there is proved, 1st. by the natural and constant absorption of fat and serum; 2d. by the more manifest one that produces resolution of serous infiltrations in dropsies, sanguineous in ecchymosis, purulent in the different kinds of abscesses that are removed; 3d. by the disappearance of mild fluids injected into these cells, an effect that must be owing to the agency of these vessels; 4th. by the resolution of natural and artificial emphysema, in which the air, or at least the principles that constitute it, have no other way of escaping. This is evident when the emphysema arises from a rupture of a bronchial cell, and when a very little opening is made in the animal, it is stopped after the air is driven by it into the sub-cutaneous texture; this I have convinced myself of. 5th. The drying up of external ulcers is owing to the cellular absorbents. Oftentimes in phthisis the ulcers are suddenly emptied, and we find in the subject who dies immediately, only the place that was occupied by pus or sanies; I have already known two patients to die in this way by a re-absorption almost instantaneous and exactly analogous to that of external ulcers. 6th. Where there is the most cellular texture, we meet with the greatest number of absorbents, and the most of those bodies with a glandular appearance, in which these vessels ramify. Where the cellular texture is scarcely discoverable, as in the brain, we can with difficulty see the absorbent system, &c.
We must consider, then, the cellular system as the principal origin of the absorbents, of those especially which serve to carry the lymph. These vessels and the exhalants appear to contribute particularly to the formation of its structure. Many have thought that it was exclusively formed of them; but this is not founded either upon observation or dissection. We see a transparent filamentous texture, and nothing more. Each cell is a reservoir intermediate between the exhalants that terminate and the absorbents that arise there. They are in a small way what the serous sacs are in a large one. We do not see the orifice of either set of vessels.
Nerves.
We see many nerves running through the cellular texture. But do these filaments stop there? Dissection affords no light upon the subject; it arises perhaps from this, that these filaments being white like the texture, we cannot see them at their termination as well as we can the arterial branches, which are rendered apparent by their colour, when they contain red blood.