STUDIES ON THE CONNECTIVE TISSUE OF THE COCK COMB: I. HISTOCHEMICAL OBSERVATIONS ON THE GROUND SUBSTANCE

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Abstract
1. The ground substance of the mucoid layer of the cock comb has been found to show a strongly metachromatic reaction with toluidine blue, but the PAS reaction was negative. The fibrils, which do not stain metachromatically, show a significant PAS positivity. The metachromatic ground substance is very easily soluble in water, while the PAS positive substance of the fibrils is more resistant to extraction. The metachromasia of the ground substance disappears below pH 3.0. No metachromasia could be observed on sections previously treated with gelatin solution. In the capon comb the PAS positivity is restricted to the thick collagen bundles and no metachromatic ground substance is present. 2. The uptake of toluidine blue by the comb tissue was determined quantitatively. The values obtained with sections of the cock comb are about 15 µg/mg. wet tissue, decreasing to about 3 µg/mg. after extraction with dist. water. The capon comb bound about 2-3 µg toluidine blue per mg. wet tissue. 3. Hexosamine determinations on slices of the whole cock comb gave dry weight values of about 4%, while the mucoid layer alone yielded 1½ to 3 times higher values. After extraction with dist. water, the cock comb tissue loses about 75% of the total hexosamine. In the capon comb, a hexosamine content of about 0.5% was found; this value was not influenced by previous dist. water extraction. 4. The water content of the defeated cock comb was found to be about 89% of the dry weight; that of the isolated mucoid layer was even higher (90 and 94%). The water content of the capon comb is about 75%.