Carbonic Anhydrase in the Mamillæ of the Hen's Egg Shell

Abstract

THE shell of the hen's egg is formed in the oviduct of the hen within 19 h, and in this shell 5 layers can be morphologically differentiated. From the inner to the outer layer are, in consecutive order, the inner egg membrane, the outer egg membrane, the mamillæ, the matrix, and, finally, the cuticle. The egg which passes into the uterus is already covered by the inner and outer egg membranes; but whether the mamillæ are already formed in the isthmus or only later in the uterus has not been definitely established. The mamillæ and the egg shell matrix which are formed in the uterus are consequently incrusted with an inorganic substance which consists mainly of calcium carbonate. The porous cuticle finally surrounds the calcined egg shell on the outside. The CO₃⁻⁻ ion as well as the calcium is of equal significance in the calcification process of the egg shell.