Mammary Glands of Pregnant Rats: Development Stimulated by Licking

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Science  18 Mar 1966:
Vol. 151, Issue 3716, pp. 1403-1404
DOI: 10.1126/science.151.3716.1403


At the end of gestation, the mamnmary glands of pregnant rats that have been prevented from licking their ventral surfaces by neck collars are about 50-percent less developed than those of control animals. Neither the burden nor the stress ejfect of the collar is an alternative explanation. A considerable proportion of mammary development during pregnancy is thus caused by the female's own licking.