VI. EFFECTS OF DEFICIENCY 237 



usual tissue fixation and staining appears quite homogeneous is found to 

 show a fibrillar network lying in a homogeneous matrix; this network is 

 made up chiefly of a protein, collagen, and the matrix itself contains a poly- 

 saccharide, probably chondroitic sulfuric acid. The collagen fibers show a 

 definite periodicity of bands in their structiu'e with finer bands within the 

 periods. These collagen fibers resemble those found in skin, where the 

 chemical composition has been studied extensively and fascinating theories 

 concerning the arrangement of their chemical groups have been proposed 

 that may account for some of their physical properties. 



The homogeneous matrix is also being studied and among other proper- 

 ties shows the property of metachromasia. This is present in the cartilage 

 matrix and seems concentrated about the hypertrophic cartilage cells; it is 

 probably due to the peculiar effect of the polysaccharides upon the specific 

 dye (polymerization). 



The osteoblasts have been shown to contain lipids, glycogen, phospha- 

 tase, and lecithinase. Cytochromic oxidase has been demonstrated in the 

 osteoblasts in addition to ribonucleic acid and its enzyme, ribonuclease. 

 Less is known about the chemical composition of cartilage cells, but alkaline 

 phosphatase, phosphorylases, glycogen, lipoids, and lecithinase have been 

 demonstrated in these cells as well as some oxidases. 



The reactivation of dormant osteoblasts in the scorbutic animal treated 

 with vitamin C has yielded valuable information concerning the mechanism 

 of synthesis of cell cytoplasm. Under the influence of ^dtamin C cell cyto- 

 plasm is synthesized: alkaline phosphatase reappears, protein synthesis is 

 accelerated, and cells become filled with ribonucleic acid and ribonuclease 

 and glycogen. 



The electron microscope has revealed the location and orientation of 

 mineral crystals on the collagen fibers as well as their configuration.^^ 



The mechanism of bone resorption remains as obscure as ever, although 

 the local application of parathormone can initiate and maintain such re- 

 solution by stimulating osteoclastic activity. Osteoclaats can bring about 

 the resorption of both calcified and uncalcified cartilage matrix as well as 

 osteoid tissue. Just how the mineral matter is made to disappear during the 

 process of reabsorption of calcified trabeculae is not clear. Inorganic crystals 

 have been demonstrated in the osteoclasts. This is very rare, however, and 

 the mechanism of action of both osteoblasts as well as osteoclasts in the ab- 

 sorption of bone is finite obscure. Tension seems to affect enzyme activity, 

 a fact to bear in mind in explaining the effect of tension in molding bone. 



The chief consequence of vitamin D deficiency is the disruption of the 

 orderly processes of bone formation which we have briefly described. In the 



69 R. A. Robinson, Trans. 3rd Conf. Mclaholic Interrelations pp. 271-289 (1951); 

 R. A. Robinson, Trans. 5lh Conf. Metabolic Interrelations 1953 (In press). 



