OP NON-VASCULAR ANIMAL TISSUES. 163 



for its circulation throughout the mass of the cartilage ; their presence is especially 

 required in this particular form of cartilaginous structure, from the great degree of 

 density which it possesses. 



1. Articular Cartilage. 



Articular cartilage is situated either on the rounded extremities of long bones, or 

 on the surfaces of flat and irregular bones. The portion of bone upon which it rests, 

 is in some instances formed by the ossification of a distinct cartilaginous epiphysis. 

 In non-epiphysal bones, the extremity of the shaft of the bone performs the same 

 functions with regard to the articular cartilage situated upon it, as do the epiphyses 

 in those bones which are provided with them. There is this difference in articular 

 cartilage, with regard to its nutrition during and after its development ; that in the 

 former state there is no positive separation of it from the cartilage which is subse- 

 quently converted into bone, and in which its nourishing vessels are contained; 

 whilst, in the latter state, these vessels are separated from it by an osseous lamella. 

 The free surface of articular cartilage during, as well as after, its development, is 

 covered by synovial membrane, to which it is attached by cellular tissue. 



Around every joint, from a very early period of development, there are found 

 numerous arteries and veins, " the articular vessels," by which their nutrition is 

 effected. 



With respect to vascularity, the nutrition of articular cartilage during its de- 

 velopment may be divided into two stages ; viz. the early one, during which no 

 vessels enter any of the structures of the joints; and the subsequent one, in which the 

 cartilage of the bone on the one surface, and the synovial membrane on another, are 

 supplied with blood-vessels. In adult age, after development is completed, the same 

 vessels continue the process of nutrition ; those of the bone being situated in the 

 cancelli, as before described, whilst those of the synovial membrane are considerably 

 diminished in size. 



In order to illustrate the nutrition of cartilage during its earliest stage, I have 

 made the following dissections. 



A. The First Stage of Development of Articular Cartilage. 



Dissections of Articular Cartilage during the more early periods of foetal develop- 

 ment, before Blood-vessels enter into any of the Structures of the Joints. — a. In a foetal 

 Calf, which measured twelve lines from the vertex of the head to the commencement 

 of the caudal vertebrae, the rudiments of the shaft of the os femoris were wholly car- 

 tilaginous, and measured one line in length. 



The corpuscles or cells of which this cartilage was composed, were large, round, 

 and loosely connected together. 



MDCCCXLI. z 



