BONE CELLS AND BONE RESORPTION 477 



Distinction between the Matrices 

 of Calcified Cartilage and Bone 



Calcified cartilage was readily distinguished from bone in ribs and 

 tibiae by the absence of cells (Fig. 1), and by staining differences 

 with all histological procedures used. In ultrasoft x-ray microradio- 

 grams, the matrix of calcified cartilage was sharply demarcated from 

 that of bone by its considerably reduced organic mass content (Figs. 

 6 and 7 ) . However, no appreciable differences were detected in the 

 degree of calcification of these two matrices in the soft x-ray micro- 

 radiograms prepared from undecalcified sections ( Fig. 19 ) . 



Distinction between Woven and Lamellar Bone 



Woven bone could be distinguished from lamellar bone (most 

 easily in the skull) owing to differences in the matrix which are re- 

 flected in increased basophilia, in greater irregularity of the collagen 

 bundles ( Figs. 2 and 12 ) , and in affinity for the PAS reaction ( Figs. 

 4 and 22). Furthermore, in woven bone osteocytes were generally 

 larger, closer together, and more irregularly arranged ( Figs. 2, 4, 5, 

 11 to 14). Woven bone, in contrast to lamellar bone, was also char- 



FiG. 1. Metaphyseal trabecula from the tibia of a 10-day-old rat. Note the 

 unstained core of calcified cartilage matrix. The canaliculi of osteocytes situated 

 within the surface coating of bone do not penetrate the cartilage. Bodian's 

 silver. (X 800.) 



Fig. 2. Parietal bone of a 26-day-old rat, showing regions of woven (w) 

 and lamellar (/) bone. Note the differences in the arrangement of collagen 

 fibers and in the distribution of osteocytes in these two types of bone matrix. 

 Gomori's silver. (X 800.) 



Fig. 3. Tibial metaphysis of a 26-day-old rat, illustrating normal, sub- 

 periosteal resorption accompanying remodeling of the "funnel" region. Note 

 that osteoclasts (right) are engaged in the simultaneous resorption of calcified 

 cartilage (arrow) and bone. Gomori's silver, (x 200.) 



Fig. 4. Part of the parietal bone, near the parietal suture, in a 17-day-old 

 rat. A segment of woven bone, stained heavily with periodic acid-Schiff, is 

 indicated by an arrow. The boundaries of the diploic spaces are unrelated to 

 the distribution of either woven or lamellar bone. PAS-hematoxylin. (X 200.) 



Fig. 5. Ultrasoft x-ray microradiogram of the region shown in Fig. 4. Note 

 the greater organic mass of lamellar bone as compared with woven bone. 

 (X200.) 



