340 



CLXXVIII. Of the articulations, the articulating cartilages and liga- 

 ments^ and the synovial fluid. The articulations of the different parts of 

 the skeleton are not all intended to allow of motion, several, as the ser- 

 rated and squamous sutures, and the gomphosys, are entirely without 

 motion, and are, on that account, termed synarthrosis. All the other ar- 

 ticulations, whether the bones are in immediate contact (diarthrosis of 

 contiguity,) whether they are united by a substance interposed between 

 them (diarthrosis of continuity or amphiarthrosis,) are endowed with a 

 certain degree of mobility. I shall speak merely of the moveable articu- 

 lations ; whether they allow of extensive motions and in every direction 

 (diarthrosis orbicularis,) or whether the bones move only in two opposite 

 directions (alternate diarthrosis or ginglymus,) by forming an angle (an- 

 gular ginglymus,) or by executing, on each other, motions of rotation 

 (lateral ginglymus.) 



In all the articulations, the osseous surfaces are covered by lamina of 

 a substance less hard than that of the bone. These are the articulating 

 cartilages which answer the two purposes of giving to the ends of the 

 bones, the degree of polish necessary to their slipping freely, and to fa- 

 cilitate motion, by the considerable degree of elasticity which they pos- 

 sess. Morgagni has shown, that of all animal substances, cartilages pos- 

 sess most elasticity ; their sturucture is very different from that of the 

 bones, even when these are yet cartilaginous; for, these articulating car- 

 tilages do not become ossified, even in persons greatly advanced in 

 years*. They are formed of very short fibres disposed according to the 

 length of the bone, strongly compressed against each other, and united 



stance may be easily detached from the bone. It resembles, in some respects, a cob- 

 web, being pierced by a number of holes. It is formed of cellular tissue, and of vessels. 

 The former is very delicate and rare ; and evidently performs the function of furnish- 

 ing a surface for the ramification of the vessels. Some of these vessels are ramified ex- 

 ternally, proceeding directly from the medullary membrane to the osseous texture sur- 

 rounding' it, and thus performing the office of an internal periosteum to the bone; 

 others are distributed internally, and in the direction of the axis or the bone, to the me- 

 dullary membrane itself, and to the spongy extremities of the bones. The principal 

 artery of the medullary canal is surrounded by absorbent vessels at its entrance into this 

 canal. A plexus of nerves may be also observed to surround the artery in the same situ- 

 ation, and to dip into the bone at the place nearest to the arterial trunk. 



The adipose vesicles, which contain the marrow and occupy the interior of the medul- 

 lary membrane, are the same in kind as those of the cellular texture, although less dis- 

 tinct. Authors have long since considered that those adipose vesicles are united en 

 grappt, and may believe that they communicate with eacli other. 



M. BECXAKD considers the marrow to consist of seven parts out of eigl it of an oleagin- 

 ous matter, in fat subjects, which inference accords with the opinion of of GUUTZMACHEII; 

 while this substance, in a phthisical patient, was found to consist of only a fourth part 

 of fatty matter, the rest being a serous, or albuminous-like fluid. 



The marrow does not exist in the fostus, and even the medullary mebrane itself can- 

 not be recognised previous to ossification. As this process advances, the medullary ca- 

 nal begins to be formed ; and at first the nutritious artery nearly fills it. At a later pe- 

 riod this artery is seen ramified on the parietes of this cavity, and in the situation of the 

 medullary membrane. The marrow becomes abundant as age advances, owing to the 

 enlargemeut of the medullary cavity. 



The sensibility of the marrow, which was contended for by DCRVSRIVEY, but since de- 

 nied, is considered by M. BKCLARD really to exist, and to be satisfactorily shown, when 

 some time is allowed to ellipse between the pain of the operation necessary to expose 

 the marrow, and the experiment to which it is to be subjected. 



See APPKNDIX, Note H H, for additional remarks on this subject. Copland. 



* Sometimes, however, these cartilages are destroyed, the denuded bone then becomes 

 polished by friction, and as hard as ivory. Copland. 



