39. In what proportions are the atmospheric gases found in the blood?
The mean quantity of the gases contained in the human blood has been found to be equal to 1-10th of its whole volume. In venous blood, the average quantity of carbonic acid is about 1-18th, that of oxygen about 1-85th, and that of nitrogen about 1-100th of the volume of the blood. In arterial blood their quantities have been found to be carbonic acid about 1-14th, oxygen about 1-38th, and nitrogen about 1-72nd.
40. Then is nitrogen taken into the blood from the air?
Such a supposition is highly improbable. It is probably derived from nitrogenised food, just as carbonic acid is derived from carbonised food.
Venous blood is that which is returning through the veins of the body from the organs to which it has been circulated.
Arterial blood is that which is flowing from the heart through the arteries to nourish the parts where those arteries are distributed.
43. What is the difference between venous and arterial blood?
Venous blood contains more carbonic acid, and less oxygen and nitrogen than arterial blood.