3 During rest ab out 0,02 cal per minute are released from 1 cm muscle matter, whilst with extreme work load this is elevated to 50 times the resting value, i. e. approximately 1 caljmin. Aretention of this heat would mean an increase of body temperature by 1 C per min. As the heat con duction in the body tissues is rather bad, the heat release is almost solely effected through the blood flow. The circulation is regulated through the 3 3 oxygen consumption. A blood circulation of ab out 1 cm per cm muscle and minute, which is the upper limit under practical conditions, suffices to release 1 caljmin, provided that there is a difference in temperature of 1 C between the blood entering the -muscle and the interior of the muscle itself. Due to the relatively high circulation necessary to cover the oxygen demand the muscle is not in danger of being overheated, even with extreme work loads. Even if this circulation is interrupted there is no such danger, since at the same time the oxygen supply and, consequently, the heat production are discontinued. It is far more difficult, however, to maintain the heat balance of the whole body. A work load of 10 kcaljmin, which a healthy man is able to maintain for two hours, means an increase of body temperature by 5 C within 30 minutes unless the heat is released from the body. This, however, means a dangerous overheating of the body."

According to their effects on man, the author distinguishes between four different noise zones, the transition ta the next zone being characterised by the appearance of an additional effect. These are: psychic reactions, vege tative reactions, injuries ta the internal ear, and, finally, mechanical de struction of ganglion cells. The author gives examples of psychic reactions, depending not only an the nature of the noise but also an the mental attitude of the person per ceiving the noise towards its source. The most characteristic reaction is a constriction of peripheral blood vessels, followed by a decrease in circula tion in the whole body. The degree of this reaction depends an the intensity of the noise, but not an its frequency, though the width of the noi se band plays an important r8le. As ta the vegetative reactions, there is no adaptation to noise. In sleep they are stronger than in a wakeful state. Exposure ta noise for years causes persistent effects an the blood flow through the skin, but also an the heart action and the regulation of the equilibrium. Noise of more than 90 phones may prove injurious ta the auditory ap paratus. Higher frequencies are more detrimental than lower ones. The audiometric diagram allows ta distinguish between traumatic injuries and those due ta old age. Extraaural effects of noise are only ta be found among operators of jets and rockets, especially at test-stands, and may be pre vented by wearing protective devices."