Studies on the avian shell gland during egg formation: mucosal intracellular pH.

1. The intracellular pH and the extracellular fluid volume of the shell gland mucosa were determined. 2. The pH value varied little during egg formation, the overall mean being 7.11 +/- 0.02 (n = 34). 3. The lowest pH, 7.01, was found 10 h after oviposition and the highest, 7.22, 18 h after oviposition.