Jane Sharp has a lot to say about breast feeding and choosing a wet nurse. She says
‘... the mother’s milk is commonly best agreeing with the child; and if the mother does not Nurse her own Child, it is a question whether she will ever love it so well ... and without doubt the child will be much alienated in his affections by sucking of strange Milk, and that may be one great cause of Children’s proving so undutiful to their Parents.’
She could have a point - the close contact between mother and child during breast feeding is said to enhance bonding. That's if all is going well, though. If there are major problems and the mother is struggling to feed come what may, that may be counterproductive.
Jane goes on to say that many babies die because the nurses’ milk is bad. The choice of a wet nurse, she says, is crucial, and gives the following advice.
‘... beware you choose not a woman that is crooked, or squint-eyed, nor with a mishapen Nose, or body, or with black ill-favoured Teeth, or with stinking breath ... or the child will soon be squint-eyed by imitation ...’
She advocates a ‘...sanguine complexioned woman, her breasts and nipples handsome, and well proportioned ... not too tall, nor too low; not fat, but well flesht; of a ruddy, merry, cheerful, delightsome countenance. If the nurse use good Diet and Exercise, it will breed good blood, and good blood makes good milk; but let her forbear all sharp, sowr, fiery, melancholy meats, of Mustard and Onyons, or Leeks and Garlick; and let her not drink much strong drink, for that will inflame the Child, and make it cholerick: all Cheese breeds melancholy, and Fish is Flegmatick. Gross and thick air make gross blood, and heavy bodies and dull wits. Places that are near the Sea side, and Bogs, are very sickly.’