ARTICULATION. 



253 



to explain without admitting either the exist- 

 ence of the synovial membrane, or the organi- 

 zation* of the cartilages. Velpeau,f too, al- 

 though he asserts that the synovial membrane 

 " terminates at the circumference of the carti- 

 lages," furnishes us with an argument in oppo- 

 sition to his own views : namely, that no appre- 

 ciable line of demarcation can be detected 

 indicating where the synovial membrane 

 ceases. " Viewed in this way," he says, " the 

 synovial apparatus consists of surfaces, mem- 

 branes, and glandular folds, between which 

 there exists not the least interruption, and 

 the use of which is to isolate the interior of 

 the joint from the tissues which surround it." 



It will appear then sufficiently evident that 

 the weight of argument preponderates in favour 

 of the doctrine that the synovial membranes 

 line the articular surface of the cartilages, and 

 that maintains their analogy with the serous 

 membranes, an analogy which receives the 

 strongest support from the physical properties 

 of the synovial membrane, from its obvious 

 functions during health, and from the diseases 

 with which it is affected ; and I apprehend, 

 that nothing tends more fully to establish iden- 

 tity or similarity in the nature of two mem- 

 branes, than the fact of a close resemblance 

 between their morbid conditions. We may 

 add, what was long ago remarked by W. 

 Hunter, that this question as to the continuity 

 of the synovial membrane on the cartilages is 

 very similar to that as to the continuity of 

 the conjunctiva over the cornea of the eye; 

 the affirmation of which latter question, Gordon 

 considers equally an anatomical refinement as 

 that of the former. 



VelpeauJ ascribes much importance to the 

 dense and fine cellular tissue which is sub- 

 jacent to the synovial membrane and is ana- 

 logous to the subserous cellular tissue else- 

 where. This would appear to be the seat of 

 the vessels which in a state of inflammation 

 give rise to the red colour of the synovial mem- 

 brane. He particularly alludes to it as afford- 

 ing a clue by which the formation of loose 

 cartilaginous bodies in joints can be explained ; 

 these he supposes to originate in sanguineous 

 effusions into this tissue, which subsequently 

 become indurated and cartilaginous, and push 

 the synovial membrane before them into the 

 cavity of the joint. It will be remembered by 

 many readers that this opinion is very similar 

 to that of John Hunter regarding the origin of 

 these bodies. 



Allusion has already been made to the fatty 

 bodies which are found in connexion with 



' This is a bad word ; we cannot deny the orga- 

 nization of cartilages, however we may deny that 

 they are supplied with red blood. It has been said, 

 I know not with what authenticity, that cartilages 

 have become yellow in jaundice. 



t Loc. cit. pp. 172 and 174. He expresses his 

 opinion much more decidedly in the art. ARTICU- 

 LATIONS, MALADIES DES. Diet, de Med. 



\ Loc. cit. v. i. p. 173. 



$ See Home's Paper, in Trans, of a Soc. for the 

 improvement of Med. and Chirure. Knowledge, 

 v. i. 1793. 



most of the Joints, and in general lying behind 

 the synovial fringes formerly described. These 

 fatty pellets were supposed by Clopton Havers* 

 to be the agents of the synovial secretion, and, 

 in consequence, have obtained much celebrity 

 under the title of Haversian glands.-]- The 

 opinion of Havers and his followers as to their 

 glandular nature was successfully combated by 

 Bichat, who proved that they were merely 

 composed of adipose substance, and in no 

 way concerned in the function of synovial 

 secretion : for 1st, the secretion of synovia takes 

 place where no such bodies exist, as in almost 

 all the bursae mucosae, and tendinous sheaths ; 

 and 2d, these bodies have no trace of glan 

 dular structure, nor are they provided with any 

 thing resembling an excretory duct ; whilst, on 

 the other hand, they possess all the properties 

 of fat. 



The synovial sac is lubricated by the sy- 

 novia, also called unguen articulare, axungia 

 articularis. How is this secreted ? We believe 

 it to be a perspiratory secretion precisely similar 

 to that of the serum from serous membranes. 

 Its formation cannot be imputed to a com- 

 bination of the serosity of the blood with the 

 fat, nor to the transudation of the marrow through 

 the extremities of the bones, nor, with Desault, 

 to a sweating from all the parts which enter 

 into the composition of the articulation, inas- 

 much as the chemical analysis of synovia 

 proves that it is essentially different from any 

 oily fluid, and does not contain a trace either 

 of elaine and stearine. 



In addition to the structures already named 

 as entering intrinsically into the formation of 

 joints, we find that the tendons and muscles, 

 which lie in the immediate vicinity of or which 

 surround the joints, contribute much to their 

 strength and security. In joints of the hinge 

 kind we generally see the anterior and poste- 

 rior parts protected more or less by the tendons 

 of muscles, and even by muscles themselves 

 passing from one segment of a limb to an- 

 other, and here it frequently happens that the 

 tendon is bound down on the bones which form 

 the member, by a fibrous expansion of great 

 strength, lined by a synovial membrane of the 

 same characters as the articular, but adapted in 

 its form to the osseo-fibrous canal in which the 

 tendon is placed, e.g. the tendons of the fingers. 

 The protection and strength afforded by mus- 

 cles is particularly evinced in the case of 

 the shoulder-joint, where the capsular ligament 

 is closely embraced by four muscles, whose 

 tendons become identified with the fibrous 

 capsule as they go to be inserted into the bone. 

 A muscular capsule, as it were, is thus provided 

 for this joint, by which the bones are main- 

 tained much more firmly and powerfully in 

 apposition than were they kept together by 

 an uncontractile ligamentous capsule alone ; 

 hence the elongation of the arm which ap- 



* Osteologia Nova : Lond. 1691. 



t Weitbrecht railed these fatty bodies, 



Adi- 



poso-glandulosae ; " and Cowper, " mucilaginous 

 glands." See them figured in Monro's work on the 

 Bursae, Tab. viii. 



