The reaction of muscles Resting muscles are weakly alkaline in reaction. In mild and even in moderate activity the reaction of these same muscles does not vary sufficiently to be detected by our most sensitive electrical methods of measuring these changes. This is due to the fact that the acids are neutralized by the buffers of the tissues and body fluids as rapidly as they are formed. During more severe and prolonged activity, however, the buffers reach the point of exhaustion and the muscles become acid in reaction. The fact that a muscle produces acid during its contraction may be shown by placing two fresh gastrocnemius muscles from a recently killed frog into two tubes of blue litmus solution. If now one muscle is stimulated electrically and caused to contract tetanically for a minute or so, the litmus solution around it begins to turn red, indicating the development of acid. Chemical analysis of the acid so produced has shown it to be lactic acid. The litmus around the resting muscle remains blue showing the presence of an alkaline reaction on the surface of the muscle. We can demonstrate the production of carbon dioxide during the contraction of a muscle by placing a frog's muscle (or entire limb) into each of two clean Erlenmeyer flasks and simultaneously aspirating the flasks in such a way that the air from each passes through a vial containing a saturated solution of barium hydroxide. This may be accomplished by a single aspirator by connecting it through a Y-tube to the two tubes leading from the bariumdroxide chambers. It will be found that during the period of the experiment the barium-hydroxide solutions become milky in color, even when both muscles are in a completely resting condition. When at complete rest, muscles respire and produce a minimum amount of carbon dioxide. In addition to this carbon dioxide given off by the muscle to the air, there is always a small amount of carbon dioxide normally present in the atmospheric air (0.03 to 0.04 per cent). This carbon dioxide reacts chemically with the soluble barium hydroxide to form the insoluble barium carbonate according to the following equation: Ba (OH) 2 + CO 2 › BaCO 3 + H 2 O If now one muscle is stimulated and maintained in a state of tetanic contraction, it will be found that a greater amount of barium carbonate and a greater turbidity will be developed in the barium-hydroxide tube connected with the flask containing this muscle. Contracting musle then produces carbon dioxide than resting muscle.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity