MUCOS/fc: 



467 



Anastomoses The ascending branches of 

 the superior profunda anastomose in the sub- 

 stance of the deltoid muscle with the anterior 

 and posterior circumflex and the cephalic branch 

 of the acromial thoracic, and with the subsca- 

 pular and the axillary branches of the thoracica 

 longior in the axilla. If the brachial artery be 

 obliterated by disease or the application of a 

 ligature above the origin of the superior pro- 

 funda, the blood will be carried by the circuitous 

 route of these anastomoses into the brachial 

 artery and all its branches from the superior 

 profunda downwards. 



When the brachial artery is obliterated near 

 the elbow, the circulation is maintained in the 

 forearm and hand by the anastomoses of both 

 profundae and the anastomotica magna with the 

 recurrent branches of the radial, ulnar, and in- 

 terosseous arteries. The anastomosis kept up 

 between all the branches of the brachial artery 

 along the periosteum of the humerus, in the 

 substance of the muscles and in the integu- 

 ments of the arm, is so free as to be sufficient 

 to ensure the circulation in the limb even if the 

 brachial artery were obliterated throughout the 

 whole of its length. 



For the BIBLIOGRAPHY, see that of ANATOMY 

 (INTRODUCTION) and of ARTERY. 



(J. Hart.) 



BRAIN. See ENKEPHALON, and NERVOUS 

 SYSTEM (CoMP. ANAT.) 



BURS^E MUCOS.&. (Fr. bourses synovi- 

 ales; Germ, die Shleimbetttel.) 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 bursae 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 excel lent 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 the head and trunk. 



Bursae mucosae, though of the same structure 

 and answering the same ends in every situation 



but gives off the interosseous high up, which has 

 all the appearance and many of the dangers of the 

 high bifurcation. Mr. Harrison mentions a case 

 in which the brachial divided into three branches, 

 two of which united to form the radial, which gave 

 off the anterior interosseous, the posterior being 

 derived from the third, the ulnar. Mr. Burns re- 

 marks, that when, as rarely happens, the ulnar 

 is the anomalous branch, the bi:urcation generally 

 takes place nearer the axilla, than when the radial 

 is the abnormal vessel. ED.] 



where they occur, may nevertheless be divided, 

 with advantage, into two great classes; viz., 

 I. the subcutaneous burste, or those placed be- 

 tween the skin and fascia; and, II. the deep 

 bursa, or those which lie beneath the latter 

 membrane. 



I. The subcutaneous or superficial burs<s 

 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 patellae ; 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 bursae 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 traversed by numerous fila- 

 ments : the appearance indeed is extremely 

 similar 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 bursae 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 bursa, or those placed beneath 

 the fascia, are much more numerous and much 

 better marked than the preceding. They are 

 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 bursts, 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. (See Jig. 11 1, 6.) On 

 opening into its cavity, it is found to con- 

 tain a viscid fluid, more or less abundant, 

 and this is sometimes traversed by fila- 

 ments passing from one wall of the sac 

 to the other. They generally occur in the 

 neighbourhood of the great articulations of 



2 ii 2 



