ORGANS OF THE BODY. 571 



the costal cartilages with the sternum from the "second to the seventh rib. 

 We not unfrequently meet in the symphyses with a layer of calcified car- 

 tilaginous tissue in the vicinity of the bone. The further consideration 

 of these parts must be left to works on descriptive anatomy. 



As regards the joints, we have already considered their cartilages ( 107), 

 and in 109 their labra cartilaginea, sometimes present. 



Under the cartilaginous coverings of bones forming joints we very 

 generally find a layer of peculiar undeveloped osseous tissue. It is, on 

 an average, 0'27 mm. in thickness (Koelliker), and consists of a yellowish 

 and usually fibrous solid mass, which presents, however, neither Haversian 

 canals nor bone corpuscles. Instead of these, we observe in thin sections 

 cartilage capsules filled with air. 



A description of the tissue of the synovidl capsules will be found in 

 135. The latter are very vascular, and are richly supplied, apparently, 

 with lymphatics (Teiclimann). They are strengthened externally by the 

 'addition of strong fibrous tissue. Their epithelial lining has been already 

 discussed, as far as it occurs, in 88, and the synovia itself in 97. For 

 a description of the inter-articular cartilages those disks of connective- 

 tissue cartilage attached laterally to sy no vial capsules, and interposed 

 between the heads of bones forming joints compare 109. The liga- 

 ments of joints consist of connective or fibrous tissue ( 135). 



From the frequent deposit of fat-cells in the connective-tissue envelop- 

 ing synovial capsules, it is often found, as already alluded to in 122, 

 that collections of the former are protruded into the cavity of the joint in 

 the form of duplicatures. These are most usually met with in the knee 

 and hip joints, and are known there as the glands of Havers. The appear- 

 ance, however, of very vascular fringed folds of synovial tissue is of far 

 more frequent occurrence, and encountered in almost all joints. These 

 are usually destitute of fat-cells, and present occasionally a few cartilage 

 elements intermixed with those of the connective-tissue. They have been 

 given the name of plicce vasculosae (1), and are represented also in the half 

 joints, according to Luschka, although devoid of vessels in those situations. 



REMARKS (1). The structures in question are frequently covered with smaller pro- 

 cesses, leaf-shaped or membraneous, and sometimes of the strangest shapes. From 

 these the loose cartilages found at times in the interior of joints are derived, though 

 not exclusively. They consist of more or less calcified cartilage, and occur most 

 frequently in the knee. Compare Virchow, " Die krankhaften Geschwiilste, " Bd. i. 5, 

 449. 



289. 



As regards the blood-vessels of bone, we have to bear in mind, in the 

 first place, that the periosteum ( 135) is very vascular. It is" supplied by 

 a number of large vessels, which pierce it, however, for the most part, only 

 on their way to supply the osseous tissue beneath. It is possessed, 

 further, of finer vessels proper to itself, which are arranged in rather com- 

 plex capillary networks. 



In order the better to comprehend the arrangement of the vessels of 

 osseous tissue, let us first take one of the tubular bones as an example. 

 As we have seen above, numerous vessels from the periosteum are given 

 off to the openings of the Haversian canals ( 140), and are there arranged 

 in a long- meshed network of tubes of considerable size, which often assume 

 characters different from those of true capillaries, and belonging rather to 

 the smaller veins and arteries. Beside this, we always meet with a large 

 single or double canal in the diaphysis of such a bone, the foramen nutrl- 



