530 



SEROUS AND SYNOVIAL MEMBRANES. 



vessels at the osseous surface (the vessels to 

 which in the first instance the formation of 

 the tissue was due) seems to constitute an 

 effectual barrier to the performance of its 

 absorption by them. And since the process 

 no doubt occurs, the only remaining vascular 

 surface, or that of the synovial membrane, is 

 clearly indicated as the agent by which it is 

 effected. 



Hence, the synovial membrane possesses, 

 so to speak, a double absorptive function : 

 one, which is essentially its own, counter- 

 balancing the active progress of secretion, of 

 which it is the seat ; another, which is, as it 

 were, delegated to it by the cartilage, and is 

 the result of the physical incapacity of the 

 latter tissue. 



And in a sketch of the morbid anatomy of 

 these structures which occupies the subse- 

 quent part of this article, it will be seen that 

 the mutual dependence thus supposed to 

 exist between the articular cartilage and 

 synovial membrane in health, finds, in all 

 probability, a close parallel in some forms of 

 disease. The chief difference noticeable 

 here is, that the preliminary breaking up of 

 structure which appears to be chiefly physi- 

 cal or attritional in the normal cartilage, is a 

 vital process which is inherent to the diseased 

 texture. 



The subcutaneous and subtendinous burses 

 present a similar fluid, which is usually in 

 much smaller quantity. They seem, in most 

 of the preceding respects, placed midway be- 

 tween the serous and synovial membranes ; 

 but many of the preceding remarks, mutatis 

 mutandis, are applicable to them. 



The close resemblance of the choroid 

 plexus to the synovial fringes was pointed 

 out in speaking of the former structure : but 

 it is obviously almost impossible to conjec- 

 ture a similar mechanical import of its secre- 

 tion ; nor, indeed, have we any reason for 

 asserting the separate existence of a fluid 

 secreted by it. 



In respect of their internal situation, all 

 the preceding tissues resemble that recondite 

 class of structures, the glands without ducts ; 

 and their similarity of form has also a physio- 

 logical parallel; viz, that all their consti- 

 tuents are returned into the blood, either 

 unchanged in their composition, or elabo- 

 rated, or effete. They differ from them, 

 however, both in the greater perfection or 

 maturity of their cell-form, and in the lesser 

 activity of their secerning power. 



In the degree, and perhaps in the nature, of 

 this resemblance, some distinctions may be 

 drawn. Thus, the serous membranes, in the 

 possession of a solid attenuated epithelium, 

 and in the probable absence of a secretion, 

 are at the lowest or most distant extremity 

 of the scale ; raised very little above areolar 

 tissue. The synovial membrane, with its 

 much more active cell-growth, and its fluid 

 secretion, comes somewhat nearer; albeit, 

 the secretion seems mainly developed in 

 answer to the mechanical requirement of a 

 lubricating fluid. Still, the possibility of a less 



physical function of both these tissues must 

 not be lost sight of. In the choroid plexus, 

 the approximation is made yet more close by 

 the negation of this mechanical import; and 

 we are left in complete doubt, whether it is a 

 provision for quantitative or qualitative fluc- 

 tuations in the blood which supplies it ; 

 whether, in either of these cases, the cell- 

 growth operates a chemical change or elabo- 

 ration on the materials submitted to its action ; 

 or, finally, whether it returns these to the 

 circulation, or surrenders them at once to the 

 neighbouring nervous tissues. 



MORBID ANATOMY OF SEROUS AND SY- 

 NOVIAL MEMBRANES. The following sketch 

 of the diseased appearances of these tissues 

 is necessarily limited to their more general 

 features. At present, it is scarcely possible to 

 discriminate between the very analogous pa- 

 thological conditions of the two classes of 

 serous and synovial membrane ; although it is 

 probable that an advance of knowledge will at 

 no distant date enable us to do so. And 

 even where the distinctions of appearances 

 are sufficiently palpable, our ignorance of their 

 general nature allows few inferences to be 

 drawn from these varieties. 



Thus, the remarkable immunity from me- 

 chanically-produced effusions which the syno- 

 vial membranes enjoy is little understood, 

 although one may perhaps doubt whether it 

 is quite so complete as it is generally sup- 

 posed to be. The only conjecture that 

 seems at all probable is, that the nature and 

 activity of the cell-growth which covers their 

 surface may have some relation to the diffi- 

 culty with which such fluids transude. So, 

 also, the comparative infrequency of adhesion 

 in their inflammations is, at present, a vague 

 fact, the cause of which is unknown; it 

 may either be referred to an explanation 

 similar to the preceding, or may, as Profes- 

 sors Todd and Bowman suggest*, depend 

 upon the presence of a viscid secretion in 

 their interior. 



Serous or dropsical effusions. One of 

 the most frequent of the morbid appearances 

 seen in these tissues is the presence of a 

 serum-like fluid in their cavity. It occurs in 

 a very large number of deaths from various 

 diseases. In most instances, however, the 

 serous membrane only shares in a dropsy 

 which is common to other structures, and 

 especially affects the areolar tissue. Thus, 

 for instance, where death has resulted from 

 some mediate or immediate obstruction to 

 the passage of blood through the right cavi- 

 ties of the heart, and has been preceded for 

 some time by general anasarca, it is usual to 

 find a considerable quantity of fluid occupy- 

 ing the pleura, peritoneum, and other serous 

 membranes. In other diseases, as in cirrhosis, 

 the serous effusion is not only a more direct 

 result of a greater venous obstruction, but 

 it also assumes a higher import than in the 

 previous instance, and becomes both of 

 earlier occurrence in the history of the dis- 



* Physiological Anatomy and Physiology of 

 Man, vol. i. p. 131. 



