210. If the blood of a human being, or of an animal whose blood gushes forth when its large vein is cut, transfers to the animal whose blood does not gushes forth, in a way that it becomes the part of its body, the blood becomes Pak. This process is called Intiqal. So, blood of a human being sucked by a leech will be Najis, because it is not considered as part of its body – it is considered as human blood.
211. If one kills a mosquito which has sat on one's body, and does not know whether that blood which has come out from it is from itself or from the person, it will be considered Pak; similarly, if one knows that the blood has been sucked from his body but has become the part of mosquito’s body. However, if the time gap between its sucking and it being killed be very short, that it considers to be the blood of a person then it will be considered Najis. And, if one knows that the blood is sucked from his body, but doubts whether it has become the part of mosquito’s body or not, as precautionary measure, one should avoid such blood.