Quran on Animals
(And verily! In the cattle, there is a lesson for you. We give you to drink of that which is in their bodies, from between the undigested food and blood, pure milk; palatable to the drinkers.) (16:66)
Maurice Bucaille said:
'From a scientific point of view, physiological notions must be called upon to grasp the meaning of this verse. The substances that ensure the general nutrition of the body come from chemical transformations which occur along the length of the digestive tract. These substances come from the contents of the intestine. On arrival in the intestine at the appropriate stage of chemical transformation, they pass through its wall and towards the systemic circulation. This passage is effected in two ways: either directly, by what are called the 'lymphatic vessels', or indirectly, by the portal circulation. This conducts them first to the liver, where they undergo alterations, and from here they then emerge to join the systemic circulation. In this way everything passes through the bloodstream.
The constituents of milk are secreted by the mammary glands. These are nourished, as it were, by the product of food digestion brought to them via the bloodstream. Blood therefore plays the role of collector and conductor of what has been extracted from food, and it brings nutrition to the mammary glands, the producers of milk, as it does to any other organ.
Here the initial process which sets everything else in motion is the bringing together of the contents of the intestine and blood at the level of the intestinal wall itself. This very precise concept is the result of the discoveries made in the chemistry and physiology of the digestive system. It was totally unknown at the time of Prophet Muhammad and has been understood only in recent times. I consider that the existence in the Quran of the verse referring to these concepts can have no human explanation on account of the period in which they were formulated.'31