Page:Popular Science Monthly Volume 40.djvu/844

822 Another light is thrown upon the waste poisons of the tissues by the statement that they exhaust the power of muscle to contract. Muscle taken from a freshly killed animal, if fed with arterial blood, or blood supplied with oxygen, may retain for some time its power of contraction. But if venous blood (blood that has lost its oxygen and is charged with waste poisons) be injected into it, the power of contraction is lost quicker than if no blood be supplied to it. In the same way the power of the muscle is soon exhausted if a solution containing substances which can be extracted from muscle (such as kreatin, lactic acid, etc.) be injected into it (M. Foster, page 150). These facts help us to see the local mischief which must often arise from these poisons, as well as their effects on the nerve-centers. Many an ache and pain are probably due to local effects of the waste poisons, whether they are the normal waste poisons of the system, which under unhealthy conditions of life we are not properly getting rid of, or the special waste poisons of skin and lungs that we have rebreathed into the system.