SEROUS AND SYNOVIAL MEMBRANES. 



521 



referred to it for a statement of the arguments 

 on both sides of this interesting question up 

 to that date. (See ARTICULATION.) 



The rapid progress of histological anatomy, 

 and the use of the microscope, have since 

 thrown much light on the subject, yet perhaps 

 with a less immediate effect than might have 

 been anticipated. 



Fig. 401. 



V 



VlUus-shaped process from the free Margin of the 

 Alar ligament. From the Cat. (Magnified 300 

 diameters.} 



From the impossibility of injecting the 

 vessels of the synovial membrane beyond the 

 margin of the cartilage, it had long been 

 known that they did not extend over this 

 articular surface ; and one might almost 

 imagine that a looped termination of the 

 vessels in this situation must have been sus- 

 pected. And the researches of Mr. Toynbee* 

 concerning the vascular arrangements of the 

 deep or osseous surface of the cartilaginous 

 lamina, showed a similar disposition of the 

 vessels in this situation. Everywhere a thin 

 plate of bone, impermeated by vessels, sepa- 

 rates them from actual contact with the car- 

 tilage ; and the capillaries themselves, as they 

 approach this osseous lamella, appear some- 

 what dilated, and finally, taking an arched 

 course, they return upon themselves into the 

 neighbouring extremity of the bone. The 

 truth of this description as a whole is readily 

 tested and confirmed by examining any part 

 of the substance of a diarthrodial cartilage. 

 Such a fragment, torn up in any manner, 

 and submitted to a sufficiently high magnifying 



* Philosophical Transactions, 1841. 



power, evinces no trace whatever of vessels, 

 or of their easily recognisable contents. 



But although the absence of vessels is thus 

 proved, the absence of the synovial membrane 

 by no means necessarily follows. The less 

 so, indeed, that modern physiological research 

 exhibits almost all structures as essentially 

 extra-vascular : i. e. it shows that in almost 

 all, the characteristic substance of their tissue 

 is separated from their vessels by an interval ; 

 an interval which, though always minute, is 

 nevertheless an appreciable, and often a 

 measurable one, and which the pabulum de- 

 rived from the blood has to traverse in order 

 to effect their nutrition. 



The continuity of the synovial membrane, 

 or the reverse, can only be settled in one 

 way ; to wit, by an appeal to observation : 

 and since the naked eye fails to give sufficient 

 information, it remains to the microscope to 

 decide its presence on, or absence from the 

 articular surface. 



Henle* affirms the continuity of the mem- 

 brane over the cartilage, as a tesselated epi- 

 thelial covering of nucleated cells, resembling 

 those which line the serous membranes and 

 the other parts of the joint. 



Professors Todd and Bowman in their 

 more recent workf, state that they have been 

 unable to detect such a covering in the adult, 

 but that, on the contrary, they have usually 

 observed an irregular surface, presenting no 

 cells beyond the ordinary scattered corpuscles 

 of the cartilage. In the foetus, however, they 

 have found it readily visible. 



A comparative examination of those car- 

 tilages in different genera of animals, or in the 

 same animal at different stages of life, partly 

 confirms, partly modifies, each of these state- 

 ments. 



In a specimen of diarthrodial cartilage, taken 

 from an adult mammal, if we make a thin section 

 parallel to the articular surface, and look 

 directly upon this part of the interior of the 

 joint, we see appearances similar to those 

 represented in Jig. 402. A number of cartilage 

 corpuscles, at irregular distances from each 

 other, and separated by the intercellular sub- 

 stance of this tissue, constitute the only 

 cell-formation visible, and the existence of 

 similar corpuscles at varying depths in the 

 substance of the cartilage may easily be 

 verified. The chief difference noticeable 

 between the deeper and more superficial of 

 these cells is, that those in the latter situation 

 contain in their interior many yellow and 

 highly refractile granules, which are of com- 

 paratively uniform size, and occupy their 

 cavity about midway between their tolerably 

 central nucleus and the inner surface of the 

 cell-membrane. This appearance becomes 

 still more manifest as the corpuscles approach 

 the articular surface. A thin vertical section 

 of the cartilage shows that the cells are in 

 greater numbers near this surface, and the 

 edge which borders the joint exhibits an irre- 



* Allgemeine Anatomie, S. L'-JI'., ct seq. 

 f The Physiological Anatomy and Physiology of 

 Man, vol. i. p. 90. 



