250 ON THE SOURCE OF MUSCULAR POWER. 



oxygen is the condition of muscular action." Finally, in a masterly 

 review of the present relations of chemistry to animal life, published 

 in March last,* Odling says, page 98, " Seeing, then, that muscular 

 exertion is really dependent upon muscular oxidation, we have to con- 

 sider what should be the products, and what the value of this oxida- 

 tion." . . . And again, page 103, "The slow oxidation of so 

 much carbon and hydrogen in the human body, therefore, will always 

 produce its due amount of heat, or an equivalent in some other form 

 of energy ; for while the latent force liberated by the combustion of 

 the carbon and hydrogen of fat is expressed solely in the form of 

 heat, the combustion of an equal quantity of the carbon and hydro- 

 gen of voluntary muscle is expressed chiefly in the form of motion.''^ 



Nevertheless, this view of the origin of rhuscular power has not 

 escaped challenge. Immediately after its first promulgation, Dr. J. 

 E. Mayer wrote,f "A muscle is only an apparatus by means of 

 which the transformation of force is effected, hut it is not the mate- 

 rial by the chemical change of which mechanical work is produced." 

 He showed that the 15 lbs. of dry muscles of a man weighing 150 

 lbs. would, if their mechanical work were due to their chemical 

 change, be completely oxidized in 80 days, the heart itself in 8 days, 

 and the ventricles of the heart in 2^ days. After endeavouring to 

 prove by physiological arguments that not one per cent, of the oxy- 

 gen absorbed in the lungs could possibly come into contact with the 

 substance of the muscles, Mayer says, " The fire-place in which this 

 combustion goes on is the interior of the blood-vessels, the blood 

 however — a slowly-burning liquid — is the oil in the flame of life. . 



. Just as a plant-leaf transforms a given mechanical effect, light, 

 into another force, chemical difference, so does the muscle produce 

 mechanical work at the cost of the chemical difference consumed in 

 its capillaries. Heat can neither replace the sun's rays for the plant, 

 nor the chemical process in the animal : every act of motion in an 

 animal is attended by the consumption of oxygen and the production 

 of carbonic acid and water ; every muscle to which atmospheric oxy- 

 gen does not gain access ceases to perform its functions." 



But Mayer was not the first to conceive this view of muscular 

 action. Nearly two hundred years ago, a Bath physician. Dr. John 



* ' Lectures on Animal Chemistry.' 



f ' Die organiscbe Bewegung in ihrem Zusammenhange mit dem Stoffnrechsel,' 



1845. 



