The well-trained muscles contain only healthy protoplasm, and give off but a small percentage of nitrogenous decomposition products. Let the well-fed person who takes but little exercise, run half a mile, or play a simple game of ball, and the following day the muscles will be stiff and sore; this unusual exertion has caused the breaking down of much loosely organized tissue which could have been made firm and healthy by daily muscular activity. [Sidenote: Why vegetarians have more endurance than meat eaters] Those subsisting upon a low nitrogenous diet, especially vegetarians, are affected much less by fatigue than meat eaters whose muscles contain larger quantities of unnecessary nitrogen and nitrogenous decomposition matter. [Sidenote: The diet governs the production and the accumulation of body-waste] The common laws of health demand that sufficient motion be taken every day to prevent the accumulation of carbon dioxid or waste matter throughout the body. Both the production and the accumulation of waste matter depend very largely upon the diet. All animal flesh (food) is undergoing gradual decomposition, and adds its waste matter to that of the body, therefore meat eaters require a much greater amount of exercise to maintain a given standard of blood-purity than do vegetarians. SYSTEMS OF PHYSICAL CULTURE Numerous schools of physical culture and artificial methods of exercise have flourished in all civilized countries within the past few years. This fact emphasizes the pressing need for a general change in our methods of living. The various systems of indoor exercise popularly taught are at the best weak substitutes for the more natural and wholesome forms of combined exercise and re-creation found in outdoor life and outdoor sport. Some of the methods referred to are as follows: [Sidenote: Tensing] Tensing, which consists of slow movements in which opposite muscles are made to pull against each other. The student can easily grasp the principle involved in this system, and from his own ingenuity extend it as fully as he desires. [Sidenote: Vibratory exercises] Vibratory exercises, which are somewhat similar to the tensing system; however, instead of slow movements, the arms or other portions of the body are moved with a rapidly vibrating motion. The effect produced is essentially the same as in the tensing system. [Sidenote: Heavy-weight exercises] Heavy-weight exercises, consisting in the use of heavy dumb-bells or other apparatus in which the actual physical pull exerted by the body in moving the weights is sufficient to try the muscles to their maximum capacity. This system of exercise should be discouraged; while it may add to the mere lifting strength, it takes from the muscles their flexibility, and from the body its agile and supple activity. [Sidenote: Indoor exercises]