BURSIE MUCOS/E. (Fr. bourses synovi ales ; Germ. die Shleimbeutel.)---This name was first given by Albinus to small shut sacs, filled with an unctuous fluid, which he found in certain parts of the body, interposed between the tendons and bones. The name, however, is now much more extensively applied, for ana tomists have ascertained that those smooth membranes, previously noticed by Winslow, covering the tendons and lining the tendinous sheaths about the wrists and ankles, are strictly of the same nature as those described by the Dutch anatomist. The number of bursm known to Albinus, and described by him in his " His toria Musculorum," was but sixteen pairs. Monro, who first properly explained their ana tomy and uses in his excellent monograph upon this subject, has made us acquainted with no less than seventy pairs, all situated in the ex tremities : and since his day the number has been further increased by the discoveries of Beclard and others : so that anatomists are now acquainted with upwards of one hundred pairs, many of them situated in tine head and trunk.
Burge mucosa; though of the same structure and answering the same ends in every situation where they occur, may nevertheless be divided, with advantage, into two great classes ; viz., I. the subcutaneous bursee, or those placed be tween the skin and fascia ; and, II. the deep bursffl, or those which lie beneath the latter membrane.
I. The subcutaneous or superficial bursx were unknown not only to Albinus, but even to Monro and Bichat ; at least there is no mention made of them in the works of any of these authors. Beclard, in his " Additions to the General Anatomy of Bichat," appears to be the first anatomist who refers distinctly to them. The most remarkable are,-1, a large one placed between the skin and the liga mentum patellw ; 2, one between the skin and fascia covering the great trochanter of the femur ; 3, one between the skin and fascia over the olecranon. These are all extremely well marked. There are others likewise, which, though less perfectly developed, are, however, evidently of the same nature ; such as that between the skin and fascia over the angle of the lower jaw, and those found upon the dorsum of the hand beneath the phalangeal and meta carpo-phalangeal articulations. These super ficial bursw are not equally perfect in all in dividuals : they are best developed in those whose limbs are actively and habitually exer cised. On cutting into their cavities we gene rally find them tmversed by numerous fila ments : the appearance indeed is 'extremely sitnilar to that presented by the subcutaneous cellular tissue in certain parts of the body,—in the palpebra and penis, for example ; and this no doubt is the reason why these bursm were not distinguished from cellular membrane by Monro and others. That they are different structures, however, or at least that they are independent of the cellular system, is sufficiently proved by the simple process of inflating their cavities through a small opening made into them ; we then find that the air is circumscribed within a definite boundary, and cannot, as in the palpebra and penis, be made to pass into the surrounding cellular membrane.
II. The deep bursee, or those placed beneath the fascia, are much more numerous and much better marked than the preceding. They am almost uniformly found in connexion with ten dons, and, generally speaking, are interposed between them and the bones over which they play. Like the superficial ones, they too are always shut sacs, in most instances of an ex tremely simple form, but in some cases much more complex ; and hence they may with pro priety be subdivided into two sets,—the vesi cular and the vaginal.
a. The deep vesicular bursa', when fully dis tended, represent each a simple globular bag, one of whose sides is in contact with the bone, and the other with one side of the tendon, without, however, enveloping it. (Seefig. 111, b.) On
opening into its cavity, it is found to con tain a viscid fluid, more or less abundant, and this is sometimes traversed by tila ments passing from one wall of the sac to the other. They generally occur in the neighbourhood of the great articulations of the hip, shoulder, knee, and ankle, but are not, as it was supposed until of late years, con fined to the extremities, for we shall presently point out instances of their occurrence both in the head and trunk. Amongst the most re markable in the inferior extremity we find, in the neighbourhood of the hip-joint, a very large one between the tendon of the psoas muscle and the capsular ligament ; a large one between the great trochanter and gluteus maximus; one between the gluteus maximus and vastus externus; one between the gluteus medius and trochanter; one between the gluteus minimus and trochanter ; one between the pectineus and femur. These are all large and regular in their existence ; but there are other smaller ones fre quently met with, particularly at the posterior part of the joint connected with the small ten dons and muscles placed there. About the knee-joint there are likewise several vesicular burszs : immediately above the articulation, be tween the extensors and front of the femur, there is an extremely large one, oftentimes ex tending several inches upwards, and still more remarkable in many instances for communi cating with the synovial membrane of the joint; a fact which has been well appealed to by the general anatomist in proof of the anatomical identity of these two structures. There is a large one, likewise, at the inner and lower part of the articulation between the tibia and the tendons of the sartorius, gracilis and semi tendinosus : posteriorly between the origins of the gastrocnemii and the bone there is also found a bursa; and a similar one between the popliteus muscle and the joint. These, like the large one in front, generally communicate freely with the articular synovial membrane. There is also a bursa generally found between the semi-membranosus and the internal lateral ligament. Around the ankle there are but few vesicular bursw : posteriorly, however, between the tendo Achillis and os calcis, there is found a very large one; and smaller ones are frequently met with connected with the flexor pollicis longus, and some of the other muscles in their passage here. In the superior extremity we find,. likewise, several vesicular burs : around the shoulder-joint there is a very large and regular one placed between the deltoid muscle and the capsular ligament ; there is one between the clavicle and coracoid process ; one between the scapula and subscapular muscle ; one be tween the subscapular muscle and the capsule. Lower down there is a bursa between the humerus and the tendons of the teres major and latissimus dorsi ; and also a bursa fre quently between these two tendons, at a little distance from their insertion. About the elbow joint there is a vesicular bursa between the tendon of the triceps and the olecranon ; one in front, between the tendon of the biceps and the tubercle of the radius : there is also one between the head of the radius behind, and the extensor muscles passing over it. Around the wrist-joint there are no vesicular bursEe of any size or importance. There is in the trunk a large vesicular bursa, usually found between the latissimus dorsi and scapula. In the head we often see a distinct bursa interposed between the two divisions of the masseter muscle.