The changes that take place under differing degrees of air pressure are not purely the result of chemical changes in the body as is maintained by some, but in all these processes we see the evidence of intelligent action which we believe is the result of the reasoning of the intelligence in the body. One evidence of this is that when the workman is brought gradually from an increased air pressure to the normal air pressure the gases that have been absorbed by the tissues under the abnormal condition will be given off through the normal channels, and less injury will be done. It is interesting to note that in Nature, man is not exposed to a greater air pressure than that at sea level; it is only under artificial, man-invented environments that the body is called upon to withstand a greater pressure than the normal. It may also be noted that without the inventions of man it requires quite a little time for man to be transported from the air pressure at sea level to that of the higher altitudes as on the mountain tops. This gives Innate Intelligence an opportunity to bring about an adaptation to this change, since the change in the pressure takes place so gradually. But with man-made inventions, such as the automobile and aeroplane, one may transfer himself from sea level to great heights where the pressure is less in a very short time. This does not allow sufficient time for adaptation to take place and is much different from the slow process of climbing the mountains. So we see that, after all, most of the necessity for immediate adaptation of the body to changed environmental conditions is the result of the work of the educated mind of man, and not the result of the laws of Nature. In Nature we seldom see the necessity for sudden or extreme adaptation. But under our present artificial means of living there are such cases, and these necessitate a study of the artificial conditions as well as a study of the Innate laws of adaptation that there may be as far as possible an educated adaptation to the environment. HUMIDITY AND TEMPERATURE OF AIR Humidity Water vapor is present at all times in the atmosphere. It is the least constant of all of the air constituents, varying greatly under different conditions. The temperature produces a greater change in the amount of aqueous vapor in the air than any other factor. There may be so much water vapor in the air that the air is spoken of as being completely saturated. This is known as absolute humidity. If there is any excess over and above this complete saturation, it is given off as dew; it is spoken of then as having reached the dew point. It must be remembered that this absolute humidity does not represent a constant amount of water vapor, for the amount of moisture necessary to produce complete saturation varies with the degree of temperature. It is erroneous to speak of the air holding water.