MEASUREMENT OF THE TOTAL AREA OF SECRETORY EPITHELIUM IN THE LACTATING MAMMARY GLAND OF THE GOAT

Abstract

A method previously described for estimating the total surface area of secretory epithelium in the half-udder (single gland) of the goat, has been re-investigated and simplified. Fifty or more fields of lobule-alveolar tissue, at a constant magnification, are projected from histological sections taken from small blocks of fixed material selected at random, against a single line representing a diameter of the field. Twice the average number of intersections which the line makes with the epithelium lining the alveoli and intra-lobular ducts, multiplied by the volume of the half-udder, and divided by the length of the line corrected for magnification, gives an estimate of the total surface area of secretory epithelium. A highly significant correlation is obtained between the surface area and average weekly milk yields in a series of glands from ovariectomized goats brought into lactation by treatment with oestrogen alone, or in combination with progesterone, or from normal goats in lactation after kidding. An overall deficiency in surface area of epithelium is typical of the glands brought into lactation artificially by the administration of sex hormones. The ratio obtained by omitting the volume of the total gland from the formula provides a useful index of alveolar size, which is commonly much larger in glands developed in response to the injection of these hormones.