Studies on the avian shell gland during egg formation: aqueous and electrolytic composition of the mucosa

The intracellular composition of the avian shell gland mucosa was studied at six stages of egg formation. 2. Total water content of the mucosa before shell calcification was 4-8 kg/kg dry weight (dw) and rose to 6-6 kg/kg dw during shell formation; 60% of the increase was intracellular and 40% extracellular. 3. The potassium concentration of the mucosa remained constant during egg formation. 4. Chloride was removed constantly from the mucosal cells during egg formation. 5. A model was constructed for the glandular cells which depicts them as primarily NaHCO3-secreting cells towards the luminal side and HCl-secreting cells towards the serosal side, their main function being to provide CO2/3- for shell formation. In this model, the columnar mucosal cells are responsible for the calcium used in shell formation.