87 The foot in lifting the body on tiptoe appears at first thought to be a lever of the second class, the body being the weight and the toe serving as the fulcrum. However, if the distance which the body is raised is compared with the distance which the muscle shortens, it is found that the _supposed_ weight has moved _farther_ than the power (Fig. 118). It will also be noted that the muscle which furnishes the power is attached at its upper end to the "weight." These facts show clearly that we are not here dealing with a lever of the second class. The foot in this instance acts as a lever of the first class with the fulcrum at the ankle joint and the toe pressing against the earth, which is the _actual_ weight. Since the earth is immovable, the body is lifted or pushed upward, somewhat as a fulcrum support is made to move when it is too weak to hold up the weight that is being lifted. In other words, we have the same lever action in the foot in lifting the body as we have when one lies face downward, and, bending the knee, lifts some object on the toes. _ 88 Walking_ is considered one of the very best forms of counter-active exercise for the brain worker (page 328). 89 The epidermis does not afford complete protection against chemicals, many of them being able to destroy it quickly. The rule of washing the skin immediately after contact with strong chemical agents should always be followed. 90 "Rough calculations have placed the number of sweat glands on the entire body at about 2,000,000." Rettger, _Studies in Advanced Physiology_. 91 Heat also leaves the body by the lungs, partly by the respired air and partly through the evaporation of moisture from the lung surfaces. Respiration in some animals, as the dog, is the chief means of cooling the body. 92 "The story is told of some woodsmen who were overtaken by a severe snowstorm and had to spend the night away from camp; they had a bottle of whisky, and, chilled to the bone, some imbibed freely while others refused to drink. Those who drank soon felt comfortable and went to sleep in their improvised shelter; those who did not drink felt very uncomfortable throughout the night and could get no sleep, but in the morning they were alive and able to struggle back to camp, while their companions who had used alcohol were frozen to death.... This, if true, was of course an extreme case; but it accords with the universal experience of arctic travelers and of lumbermen and hunters in the northern woods, that the use of alcohol during exposure to cold, although contributing greatly to one’s comfort for the time being, is generally followed by undesirable or dangerous results."—HOUGH AND SEDGWICK: _The Elements of Hygiene and Sanitation_.