A lesson in cattle
In the field of physiology, there is one verse in the Holy Quran which appears extremely significant. One thousand years before the discovery of the blood circulatory system, and roughly thirteen centuries before it was determined that the internal organs were nourished by the process of digestive absorption, a verse in the Quran described the source of the constituents of milk in conformity with scientific facts.
“Verily in cattle, there is lesson for you; We give you to drink of what is inside their bellies coming from a conjunction between the contents (of the intestine) and blood, a milk, pure and pleasant for those who drink it.” (The Quran, 16:66)
The initial event, which sets the whole process in motion, is the conjunction of the contents of the intestine and blood at the level of the intestinal wall, which produces milk. This specific knowledge was unknown to mankind at the time when the Quran was revealed to Prophet Mohammad (P.B.U.H).