The inception of lactation in the cow and goat

Abstract

Part I. The changes in amount and composition of the mammary secretions of a heifer in its first pregnancy are recorded.The most striking feature is the abrupt appearance at half-way through pregnancy of a viscous secretion consisting largely of globulin.These results are extended to the primiparous and to the multiparous “dry” goat.Colostrum is shown to be normal milk admixed with the globulin secretion.The significance of the globulin is discussed. Reasons are advanced indicating that it may be an excretion of the cell when it changes from the growth phase to the secretory phase of life.The stimulus to mammary growth is briefly discussed.A partial analysis is given of the secretion from the tubercular udder of a cow. This secretion resembles somewhat the secretions of mid-pregnancy.Part II. Instances are given of cases of premature lactation in the goat, and analyses are recorded of these secretions.These cases are discussed in the light of Part I of this paper, and their bearing on the corpus luteum theory of mammary development is considered. The sexual precocity of the goat is such that the mammary growth may in all cases have been due to luteal influences.A few cases of premature lactation in the cow are also reported.The theory that the foetus produces a hormone inhibiting lactation is shown to be unnecessary.