Difussion occurs from a high concentrated region to a low concentrated region. The velocity of diffussion is proportional to the differential of concentrations. In the lung arrives blood with low levels of oxygen while the long is rich with fresh oxygen so the oxygen flows from the lung tissues to the blood.
The other tissues consume oxygen continually them they get poor in oxygen and so the oxygen that is in the blood diffuses to the tissue that is poor in oxygen.
The contact hypothesis is a theory in psychology which suggests that prejudice and conflict between groups can be reduced if members of the groups interact with each other.
The ideal drug will have a high toxic dose and a low effective dose.
Hope this helps;-;
