Neither, as regards the primary effect, is it of subsequent importance whether air be admitted into an opened bursa or sac, a synovial sheath, or the interior of a joint. All of these structures are formed into bladders or closed cavities. They all contain a similar secretion, which is a transparent, albuminous fluid, resembling white of egg. They all are of one use, or all serve to facilitate motion. The bursa is the smallest; the synovial sheath is the next in magnitude; and joints may be much the largest. The secondary effects are proportioned to their size, but in the first instance much constitutional disturbance will attend the opening of each.

These structures are not formed to endure the presence of atmosphere; air is admitted a short time after each displays inflammation. This creates symptoms of irritability, and air will enter before we see the wound. The secondary effect is, however, most to be dreaded. Bursæ are small bladders, or closed sacs, distributed over the body, and located wherever the natural motions possibly might originate friction. Sheaths always embrace tendons, being essentially closed sacs. The secondary effects of tendinous sheaths are so much the more to be dreaded than those attending punctured bursæ, because the last generally lie loosely between highly-organized parts; whereas a sheath is partly fixed upon a tendon, and tendon, being lowly organized, is more difficult to cure when it is diseased. However, joints are much worse than the preceding two; because in these the synovial membrane is partly spread over the cartilage, which lies upon the articular surfaces of bones. Now, cartilage is the most lowly organized substance in the entire body. When disease fixes upon it the morbid condition is so slow, so irritating, and so difficult to eradicate, that science almost despairs of the issue.

The results indicated show that every effort should be made to ward off the secondary effect. Therefore, when an accident of this nature occurs, proceed with the utmost gentleness. Having procured a large sponge and a pail of milk-warm water, saturate the sponge and squeeze it dry, above the injury. Do not touch the sore, but allow the fluid, as it gravitates, to wash off all or any foreign matter. With regard to the wound, dirt seldom enters that. When it does, the suppuration which must ensue upon the accident will more effectually remove it than could hogsheads of water, however unfeelingly it might be employed.

The part having been rendered clean, the wound is to be attentively observed. When nothing but blood or serum, or thin, discolored fluid can be seen, this argues the more important structures are entire. Should there be among, and yet distinct from, those discharges, a transparent, glairy liquid flowing forth, such is absolute proof some synovial membrane has been severed. The size of the current and the abundance of the secretion are also evidences not to be despised. Probabilities may be inferred from these circumstances. If the amount of the synovia be small, there is hope that a bursa only has been interfered with; when the amount is large, it demonstrates that either a sheath is punctured or the joint itself may have been opened. Synovial cavities between bones may be larger, and are much more active than the sheaths of tendons; therefore the magnitude of the current should be observed; although, when the integrity of many parts has been destroyed, little absolute dependence will be placed upon the comparative quantity of the synovial secretion.

THE TENDONS WHICH CROSS THE OUTSIDE
OF THE KNEE-JOINT.

Explanation of No 1.

THE TENDONS WHICH CROSS THE INSIDE
OF THE KNEE-JOINT.