318 SPECIAL HISTOLOGY. 



towards it, and present beautiful transitionary forms into half 

 and wholly isolated bone-cells, which exist on the border of 

 the bone. In the interior of this cartilaginous layer, ac- 

 cording to Zaglas, there is always a narrow cavity, which 

 separates the cartilaginous layers of the two bones com- 

 pletely, or almost completely, from each other. It contains a 

 synovia-like fluid, and is bounded by smooth and even walls, 

 which differ from the rest of the cartilaginous substance in 

 their greater hardness, as well as in their structure. The 

 matrix of these cartilaginous layers, in the direction of the sur- 

 face, is finely fibrous ; the cells are all of large size (as much 

 as O035"'), with numerous secondarv cells and uncommonly 

 thick walls, so that the cavities, even of the secondary cells, 

 often appear extremely contracted ; but they do not exhibit 

 any distinct indication of pore-canals or calcareous deposit. 



The costal cartilages are invested by a strong perichondrium, 

 composed of connective tissue and numerous elastic elements, 

 which commences at the sternal end in connection with the 

 synovial membrane there existing, and at the other is con- 

 tinuous with the periosteum of the ribs. The cartilage, which 

 is in connection with this membrane by a roughened surface, 

 is of considerable firmness although elastic, pale }*ellow, or in 

 thin sections, exhibiting a transparent blue tint, internally 

 almost always, in certain spots, of a yellowish-white colour, 

 with a silky lustre. Its matrix in the latter situations pre- 

 sents a fibrous structure, and elsewhere a finely granulated 

 aspect. The outermost cells, to the depth of 006 — 01'", are 

 elongated, flattened, parallel to the surface, most usually 

 small (sometimes not more than 0'0Q&"), but sometimes 

 larger, and filled with one or even many secondary cells, one 

 placed behind the other ; more internally, without entirely 

 losing their flattened figure, they are larger (most of them 0*03 

 — O'OS'"), oval, and round, and lie with their surfaces towards 

 the ends of the cartilage, and with their long axis for the most 

 part in the direction of the radius of the transverse section of 

 the rib ; in many cases, however, they are disposed more 

 irregularly. The largest of these cells (measuring as much as 

 O'OS'", or even 0-L") are found in the fibrous spots, and they, 

 in common with all the interior cells, contain secondary cells, 

 in varying, frequently in very considerable number (as many 



