The ambiguity of the title of my previous post entitled ‘Where do breasts belong? (1)' reminded me of the ‘milk line’ – which I find may also be called the mammary ridge or mammary crest. (I did not previously known that.) This is a line along which, in humans, accessory nipples and breasts may form. Sometimes these may be fully developed and even functional. Re-reading my post title to mean ‘Where on the body do breasts belong?’ The answer is not necessarily on the front of the (female) chest.
The milk line is to be found in other mammals. Indeed, it is primarily a mammalian characteristic which in humans has largely become confined to the thoracic region. The milk line extends on both sides from the armpit to the thigh in an elongated S-shaped curve. Much the same can be seen in rats, for example. It is particularly clear when the dam is suckling numerous pups who have denuded the nipple of its surrounding fur.
There are stories of women who have breastfedfrom a nipple on their thigh. The only illustrations I have seen of this have been nineteenth-century engravings or images based on them. However, I do not believe them to have been drawn from life. The images I have seen show a child standing at its seated mother’s side drinking from the outside of her thigh. The milk line does run past the groin into the upper thigh but only the inner (medical) side of the upper thigh, not the outer (lateral) side. So although the idea of breastfeeding from a nipple on the thigh is plausible, the details as depicted in the engravings I have seen are wrong.
Often a rudimentary (or supernumerary) nipple may be seen along the milk line. This takes various forms but may show up as a small area of darker skin pigmentation on the milk line. This may be found in males as well as females. The fictional Bond villain Francisco Scaramanga (from The Man with the Golden Gun (1965)) had a third (i.e., supernumerary) nipple. Unfortunately, as depicted in the film (1974), it did not fall on the milk line. For many anatomists and zoologists, their enjoyment of the film may have been compromised as a result – everything else in the James Bond films being entirely credible, of course.
