The histochemical characterization of articular cartilage from front and hind limbs of puppies up to twenty-five weeks of age has been presented. The average mass patterns for one kilogram of fresh cartilage were as follows : Through sixteen weeks of age, the extracellular compartment consisted of 522 grams of extracellular water (H2O)E and 161 grams of extracellular solids (E)S or a total of 683 grams, leaving 317 grams for the weight of the chondrocytes (C), of which 263 grams are the chondrocyte water (H2O)C and 54 grams, the chondrocyte solids (C)s. For the older puppies, seventeen to twenty-five weeks of age, the extracellular-compartment mass was 720 grams of which 548 grams were (H2O)E and 172 grams, (E)S. The intracellular compartment or the weight of (C) was 280 grams of which 209 grams were (H2O)C and 71 grams, (C)S. Using these patterns for articular cartilage, the distribution and concentration of constituents in these tissues have been presented and discussed.
Briefly, some of the most consequential points deduced from our data on fresh articular cartilage were:
1. The total water content of the tissue decreased in amount from 80 per cent to 75 per cent as the puppies aged.
2. The connective tissue increased in amount from a value of 104 grams per kilogram to 159 grams per kilogram as the puppies aged while the chondroitin sulfate mass decreased from thirty-eight grams per kilogram to twenty-three grams per kilogram. Even though the chondroitin sulphate decreased, the connective tissue increased enough to bring up the mass of the total extracellular solids from a value of 146 grams per kilogram to 181 grams per kilogram.
3. The percentage of water in the chondrocytes was an average of 83 per cent through the sixteen-week-old group; thereafter it was an average of 75 per cent in the older groups.
4. The average concentration of potassium in the chondrocytes was fifty-three milliequivalents per kilogram of chondrocytes or sixty-six milliequivalents per kilogram of chondrocyte water. The average concentration of magnesium was thirty-five milliequivalents per kilogram of chondrocytes and forty-three milliequivalents per kilogram of chondrocyte water.
Division of Orthopaedic Surgery and the Department of Biochemistry, the University of Chicago, Chicago