On Wet Nurses and Non-Species Specific Milk
Further, it's a bad idea for a very pregnant woman to try to nurse a baby. Stimulating the nipples releases a hormone called oxytocin that does two things. First, it stimulates the body to release the milk from the breast glands. Secondly, it stimulates the uterus to contract, which means it's a significant risk of sending Mama into preterm labor. Handy thing to know in a pre-medical society if the pregnancy is overdue and the midwife needs to induce though.
So then what? If the baby's mother isn't around to nurse and the pregnant woman won't work, what about giving it milk from a cow or goat?
Attempts have been made in the past to feed babies milk from non-human species - cows, goats, etc.. Those attempts have mostly failed. There are proteins and substances in human milk that are specially formulated for human babies. Feeding cow's milk that hasn't been processed into baby formula is a surefire way to kill the kiddo or at least make her dog sick, as many of the proteins and substances in cow's milk is formulated specifically to feed baby cows, which aren't much like baby humans. The same goes for goats, cats, dogs, ferrets, and any other mammal out there. Species-specific milk is the best way to feed a baby in any species, even in today's world.
Shoot, now what?
In an era before commercially prepared baby formulas, you've really got one choice for keeping a baby alive and healthy in the absence of it's mother following birth - a wet nurse. Like I said in the post on what happens to babies in famines, anybody with nipples can breastfeed, whether or not they have ever had a baby of their own. It's easier to get things going if pregnancy has already made the changes to the breast that are required for nursing, but even a woman who has never been pregnant can breastfeed if she works at it hard enough. Finding a wet nurse who is already lactating (making milk) might be the easiest option though. Getting supply going is going to require days to weeks of stimulating the nipples, a lot. Babies nurse approximately 140 minutes in a day, and that's about how much time a woman would have to spend stimulating her nipples to get a supply of breastmilk going. Around the clock, every 2-3 hours for 10-20 minutes at a time. It's not easy, but if you're talking the life of a child, it's worth doing. In the modern age, a double, hospital-grade, electric breastpump is woman's best friend, but in the age before all those gadgets, grandmothers and aunts and neighbors still wet nursed by getting supply going the old fashioned way - literally milking the breasts until milk was made.Hand expression, the act of "milking" the breast, involves putting the fingers behind the colored portion of the nipple, press toward the chest, then compress toward the nipple, but not down toward the tip. A woman with a good supply of mature milk should be able to shoot milk across the room if she hasn't fed the baby in a few hours. Point the nipple down into a container, and you can store breastmilk for bottle, cup or spoon-feeding a baby (yes, you can cup or spoon feed a newborn).
Colostrum will "bud" out from several spots on the end of the nipple as droplets and can eventually be collected in a spoon or small cup. When a woman is starting to get a supply of milk for the first time to wet nurse, putting a baby to the breast, even another baby who already is being fed by another woman before the baby eats, will be more effective than hand expression, but with proper technique, hand expression can be more comfortable and more efficient than even the double electric breast pumps used primarily in the US today.
Standford Medical School has an excellent video that shows women with various breast types hand expressing milk for their babies, both well and premature/ill.