Assalamu alaikum wa rehmatullahi wa barakatuh
And indeed, for you in grazing livestock is a lesson. We give you drink from what is in their bellies – between excretion and blood – pure milk, palatable to drinkers. (16:66)
There are 2 important points discussed in this example.
1.The palatable and pure milk which is present in between 2 impurities(blood and excretion) as well as the ones which are surely non palatable.
The taste and purity is retained despite the presence of blood and excretion just around it.
The clear hints about the blood supply
The clear hints about the relations of the mammary glands and the intestines.
Note the picture and see the verse again.The pure milk between excretion and blood.
Another clear picture proving the truth of Holy Quran.
Exalted is your Lord, the Lord of might, above what they describe.
And peace upon the messengers.
And praise to Allah , Lord of the worlds.