72 Energy, like matter, can neither be created nor destroyed. It can, however, be transferred from one body to another and transformed from one form to another form. Whenever work is done, energy is transferred from the body doing the work, to the body upon which the work is done. During this process there may, or may not, be a transformation of energy. In turning a grindstone, kinetic energy is passed to the stone and used without transformation, but in winding a clock, the kinetic energy from the hand is transformed into potential energy in the clock spring. Then as the clock runs down this is retransformed into kinetic energy, causing the movements of the wheels. Not only is kinetic transformed into potential energy and _vice versa_, but the different forms of kinetic energy (heat, light, electricity, sound, and mechanical motion) are readily transformed the one into the other. With suitable devices, mechanical motion can be changed into heat, sound, or electricity; heat into motion and light; and electricity into all the other forms of energy. These transformations are readily explained by the fact that the different varieties of kinetic energy are but different forms of motion (Fig. 84). 73 The simplest arrangement of the parts of a gland is that where they are spread over a plain surface. This arrangement is found in serous membranes, such as the pleura and peritoneum. These membranes, however, are not called glands, but secreting surfaces. 74 In the oxidations that occur in the body it is not supposed that the nutrients are immediately converted to carbon dioxide, water, and urea. On the other hand, it is held that their reduction takes place gradually, as the reduction of sugar by fermentation, and that the wastes leaving the body are but the "end products" and show only the final results. 75 Alcohol, if used in considerable quantity, leads to cirrhosis of the liver and Bright’s disease of the kidneys, both very dangerous diseases. Dr. William Osler in his treatise, _The Practice of Medicine_, states that alcohol is the chief cause of cirrhosis of the liver. Dr. T.N. Bogart, specialist in kidney diseases, asserts that one third of all the cases of Bright’s disease coming under his observation are caused by alcohol. 76 Hall, _The Purin Bodies_. 77 Review "Main Physiological Problems," page 21.